SysDB

Arista switches have, at their heart, a database called SysDB (Chapter 7). This database contains the state information and settings for the switch, organized in such a way that every Arista process or agent can access it with ease.

Traditional networking hardware uses a monolithic software architecture. This means that there is a pretty significant risk of a bug in one section of code affecting or even bringing down the entire device. Furthermore, updating one section of code can be difficult because there can be repercussions in other areas unforeseen by the developer.

Arista’s EOS is more modular. Not only does EOS separate the networking state from the processing, but drivers, processes, management, and even security patches run in user address space, not in memory shared with the kernel. This means that almost any process can be restarted without affecting the state of the network that it controls. This also means that any agent can be upgraded without affecting traffic flow. Agents can be added with ease, and faults are isolated to their individual user spaces. Should one process crash, it cannot affect the rest of the system. Should the process crash or lock up, the EOS process manager (ProcMgr) can restart it without affecting other modules and without affecting the networking state. Because SysDB is just a hierarchy of state information and contains no application code, it is extremely reliable.

Because EOS is so modular, the drivers for the Application-Specific Integrated Circuits (ASICs) are merely agents. Because of this, EOS is the same for every switch Arista makes. There are no release trains, no hardware-specific downloads, and no hours wasted trying to find the right code. If you want EOS 4.21.1F, you download the code named EOS-4.21.1F.swi. If you have a 384-port 7508R chassis switch or a 72-port 7280R fixed-configuration switch, the software image is the same.

Using EOS

If you’ve used an industry-standard switch, you can use an Arista switch. As soon as you log in to an Arista switch, you’ll recognize the look and feel because it’s very similar to, for example, IOS. The important distinction is that it is not IOS because the internals have been completely written from scratch. Only the command-line interface (CLI) is similar.

One of the things that frustrated me when I hooked up my first Arista switch was the fact that telnet is not enabled. In its default configuration, Secure Shell (SSH) is the only means allowed to remotely access EOS. Certainly, console access is allowed, and telnet can be enabled, but in this time of Payment Card Industry (PCI) regulations, Sarbanes-Oxley, and countless other security-centric requirements, keeping telnet disabled is a good idea. As I joke in my training classes, “it’s 20-freaking-19; stop using telnet!”

For my examples, I’m connecting through the console (through a console server). Logging into EOS is as simple as it is with IOS:

Arista-7280 login: admin
Last login: Fri Sep 16 15:33:59 on ttyS0
Arista-7280>

With only simple login authentication configured, I am dropped into EXEC mode, which should look pretty familiar. At this point, I can access Privileged EXEC mode by using the enable command:

Arista-7280>en
Arista-7280#

The prompt has changed, as I’d expect it to, and I now have the power. At this point, I’ll add my own username because I like to be accountable for my actions. Actually, that’s a lie. I’m so lazy that I like to have the same username and password on every device I’ve ever configured so that I don’t need to remember them. OK, so that’s not true either, but I thought I’d configure a username just to show how the process of configuration works in EOS.

Again, this is just like the industry standard. Here, I configure from the terminal using the config terminal command, then configure my username, and then exit:

Arista-7280#conf
Arista-7280(config)#

At this point, I am in global configuration mode. By the way, notice how I didn’t type conf t? Although the CLI will take configure terminal, the terminal part is no longer necessary. Why not? I often ask the students in my class what options there are other than terminal. Usually only the old guys know the answer because we haven’t used any of them in years.

I should point out, though, that this has changed in the past couple of years with the advent of features such as config replace and config session (Chapter 9), which makes it even more interesting to me that you can still just type conf to get into configuration mode. Let’s get back to our example:

Arista-7280(config)#username GAD secret ILikePie
Arista-7280(config)#exit
Arista-7280#exit
Arista-7280 login: GAD
Password: ILikePie
Arista-7280>en
Arista-7280#

EOS does not support clear-text passwords, and there is no command service password-encryption like there is in other operating systems. EOS no longer uses MD5 for encryption of passwords, either, opting instead for the much more powerful and secure SHA512. As such, the running configuration for my user now looks like this:

username GAD secret sha512 $6$dxUPdkGx22Cn5pUd$mok04fVNTa0Z3vvFCvrpNboushWBdiJGi
waBcuiLPCAclETvUt.rfENIRbRfFv9TAZmn2JP5u1OBErznruhXu1

Now let’s try entering an abbreviated command:

Arista-7280#ro
% Incomplete command

Because that’s ambiguous, I get an Incomplete command error. I can, however, find out what commands are available in one of two ways. First, I can press the “?” (question mark) key. This will give me a list of available commands that match what I’ve entered so far:

Arista-7280(config)#ro?
role  route-map  router

I should also point out that EOS does not show you where you made an error if you make one. IOS will show you a little carrot and point out where you fat-fingered the command. Here’s an example from an old Cisco 3750:

3750(config)#routter
                 ^
% Invalid input detected at '^' marker.

EOS does not do this, instead just giving a generic Invalid Input message:

Arista(config)#routter
% Invalid input

Back to figuring out commands from the CLI, I can also press the Tab key, at which point the switch will respond with the longest match based on what I’ve typed so far:

Arista-7280(config)#rou<TAB>
Arista-7280(config)#route

Note that I did not type the word route; the switch inserted that via autocompletion when I pressed Tab. At this point I decided that it’s the router command I was looking for, so I added the r and then pressed “?”. The switch then recognized that router is a command and listed the possible associated keywords:

Arista-7280(config)#router ?
  bgp                  Border Gateway Protocol
  general              Protocol independent routing configuration
  igmp                 Internet Group Management Protocol (IGMP)
  isis                 Intermediate System - Intermediate System (IS-IS)
  kernel               Routes installed by kernel
  msdp                 Multicast Source Discovery Protocol (MSDP)
  multicast            Multicast routing commands
  ospf                 Open Shortest Path First (OSPF)
  ospfv3               OSPF Version 3
  pim                  Protocol Independent Multicast
  rip                  Routing Information Protocol
  traffic-engineering  traffic-engineering global config

I chose one of these protocols, after which the switch put me into protocol-specific mode and altered the command line to show where I was:

Arista-7280(config)#router ospf 100
Arista-7280(config-router-ospf)#

As with the industry standard, typing exit (or its nonambiguous abbreviation) got me out of the current level and popped me back up one level:

Arista-7280(config-router-ospf)#ex
Arista-7280(config)#

By typing end, or Control-Z, I was able to exit configuration mode entirely:

Arista-7280(config-router-ospf)#end
Arista-7280#

At this point I’d like to add that the EOS CLI recognizes some Emacs control characters. I am constantly amazed that even networking guys with decades of experience are unaware of these simple CLI key combinations. The following Control key combinations will have the effects listed:

Control-A

Moves the cursor to the beginning of line

Control-E

Moves the cursor to the end of line

Control-B

Moves the cursor back one character (same as left arrow)

Control-F

Moves the cursor forward one character (same as right arrow)

Esc-B

Moves the cursor back one word

Esc-F

Moves the cursor forward one word

Entering the interface command, followed by the interface name, puts you into interface configuration mode. Interface configuration mode is similar to IOS, but more robust.

Here, I’ve entered the interface configuration mode for ethernet 1:

Arista-7280#conf
Arista-7280(config)#int e1
Arista-7280(config-if-Et1)#

One of the nice enhancements to EOS is that it has no interface range command. To configure multiple interfaces at one time, simply enter them separated by either a hyphen (for a range) or a comma (for a list). In the example that follows, I’ve entered configuration mode for the interfaces e1, e2, e3, and e10. I’ve included the first three as a range:

Arista-7280(config)#int e1-3, e10
Arista-7280(config-if-Et1-3,10)#

Check out the command prompt. It doesn’t show just “range,” but rather shows what interfaces are being configured. I love this feature because I can never remember what I typed a few short seconds ago.

Here’s a super-cool feature that’s been around for a while that was shown to me by Rich Parkin, who gets named credit because I’d been at Arista for five years and didn’t know it was possible only to be shown by the new guy who blew me away with this amazing feature. Imagine that you need to apply IP addresses to a range of interfaces. Wouldn’t it be cool if you could do that in some sort of cool automated fashion? Check this out:

Arista(config)#int e1-4
Arista(config-if-Et1-4)#no switchporth
Arista(config-if-Et1-4)#ip address 10.1.{1,4}.1/24

Whoa! Curly braces? In networking?

Let’s see what this command has done by looking at the running-config:

Arista(config-if-Et1-4)#sho run int e1-4
interface Ethernet1
   no switchport
   ip address 10.1.1.1/24
interface Ethernet2
   no switchport
   ip address 10.1.2.1/24
interface Ethernet3
   no switchport
   ip address 10.1.3.1/24
interface Ethernet4
   no switchport
   ip address 10.1.4.1/24

How cool is that? The third octet has been applied starting at one and incrementing until it got to four. That’s the meaning of {1,4}. But wait; there’s more! The first two fields that we used are called start and end. You can also add a field to this bit of curly-braced madness, which is called a step. This will allow you to do things like put in only even numbers. Let’s clear the IP addresses and put in the same IP addresses, but this time the third octet will have the numbers 2,4,6,8:

Arista(config-if-Et1-4)#ip address 10.1.{2,8,2}.1/24
Arista(config-if-Et1-4)#sho run int e1-4
interface Ethernet1
   no switchport
   ip address 10.1.2.1/24
interface Ethernet2
   no switchport
   ip address 10.1.4.1/24
interface Ethernet3
   no switchport
   ip address 10.1.6.1/24
interface Ethernet4
   no switchport
   ip address 10.1.8.1/24

Want odd numbers? Start with 1, go to 7, and step 2:

Arista(config-if-Et1-4)#ip address 10.1.{1,7,2}.1/24
Arista(config-if-Et1-4)#sho run int e1-4
interface Ethernet1
   no switchport
   ip address 10.1.1.1/24
interface Ethernet2
   no switchport
   ip address 10.1.3.1/24
interface Ethernet3
   no switchport
   ip address 10.1.5.1/24
interface Ethernet4
   no switchport
   ip address 10.1.7.1/24

But wait; there’s more! You can even use this functionality to name your interfaces—and not only that, you can format the output with padding by adding a pad field. Here I’m adding a description to each interface that reads DC1-Row-XX where XX is a two-digit, right-justified, zero-padded field:

Arista(config-if-Et1-4)#desc DC1-Row-{1,7,2,2}
Arista(config-if-Et1-4)#sho run int e1-4
interface Ethernet1
   description DC1-Row-01
   no switchport
   ip address 10.1.1.1/24
interface Ethernet2
   description DC1-Row-03
   no switchport
   ip address 10.1.3.1/24
interface Ethernet3
   description DC1-Row-05
   no switchport
   ip address 10.1.5.1/24
interface Ethernet4
   description DC1-Row-07
   no switchport
   ip address 10.1.7.1/24

How cool is that? Pretty darn cool, I’d say.

Back to interface ranges, be warned that the prompt can get a bit unwieldy with long lists of interfaces because they will all show up in the command prompt:

Arista-7280(config)#int e1,3,5,7,9,11,13,15,17,19
Arista-7280R(config-if-Et1,3,5,7,9,11,13,15,17,19)#no ip address
Arista-7280R(config-if-Et1,3,5,7,9,11,13,15,17,19)#no description
Arista-7280R(config-if-Et1,3,5,7,9,11,13,15,17,19)#switchport
Arista-7280(config-if-Et1,3,5,7,9,11,13,15,17,19)#description Odd

Another nice feature of EOS is that I don’t need to exit configuration mode to run exec mode commands. I just run them, and EOS figures it all out. There is no do command necessary with EOS:

Arista-7280R(config-if-Et1,3,5,7,9,11,13,15,17,19)#sho active
interface Ethernet1
   description Odd
interface Ethernet3
   description Odd
interface Ethernet5
   description Odd
interface Ethernet7
   description Odd
interface Ethernet9
   description Odd
interface Ethernet11
   description Odd
interface Ethernet13
   description Odd
interface Ethernet15
   description Odd
interface Ethernet17
   description Odd
interface Ethernet19
   description Odd

By the way, that show active command is the same as doing a sho running-config section-name for the current section when in configuration mode, which in this case happens to be a range of interfaces.

Ooh, here’s another cool Aristacism (I totally made up that word. See Chapter 33): when specifying interface ranges, you can use the dollar sign to indicate the last interface within the range. On an Arista 7010T, this results in the following:

Arista-7010T(config)#int e1-$
Arista-7010T(config-if-Et1-52)#

On a switch that has interfaces with lanes or blades (or both) this will appear to not work:

Arista-7280R(config)#int e1-$
% Incomplete command

This is because some of the interfaces on this switch have lanes and thus are referenced (for example) as int e50/1. To use the dollar sign in the range on a switch like this you must include all of the possible fields:

Arista-7280R(config)#int e1-$/$
Arista-7280R(config-if-Et1-49/1,50/1,...,53/1,54/1)#

Notice the ellipsis in that range prompt? The developers have made it so that very long ranges are abbreviated to prevent unusable prompts.

Technically, any mode can run commands from any parent mode. If you enter commands from a different mode at the same level (interface- and protocol-specific mode, for example), the mode will switch accordingly. You cannot, however, execute child mode commands from a parent mode. For example, you cannot execute interface-specific commands from within the global configuration mode.

I was able to pipe the output of show run to include, which outputs only what I wanted to see. This behavior is similar to the grep command in Linux. There are a bunch of options for piping in EOS, which you can see by entering | ? (vertical bar, question mark) after any show command:

Arista-7280(config)#sho run | ?
  LINE      Filter command by common Linux tools such as grep/awk/sed/wc
  append    Append redirected output to URL
  begin     Begin with the line that matches
  exclude   Exclude lines that match
  include   Include lines that match
  json      Produce JSON output for this command
  no-more   Disable pagination for this command
  nz        Include only non-zero counters
  redirect  Redirect output to URL
  section   Include sections that match
  tee       Copy output to URL

Though include is similar to grep, it differs in a significant way. This distinction is important when stacking pipes. The command sho int | inc Ethernet will output the following:

Arista-7280(config)#sho int | inc Ethernet

Ethernet1 is up, line protocol is up (connected)
  Hardware is Ethernet, address is 001c.7390.93d0 (bia 001c.7390.93d0)
  Ethernet MTU 9214 bytes , BW 1000000 kbit
Ethernet2 is down, line protocol is notpresent (notconnect)
  Hardware is Ethernet, address is 001c.7390.93d1 (bia 001c.7390.93d1)
  Ethernet MTU 9214 bytes , BW 10000000 kbit
Ethernet3 is down, line protocol is notpresent (notconnect)
  Hardware is Ethernet, address is 001c.7390.93d2 (bia 001c.7390.93d2)
  Ethernet MTU 9214 bytes , BW 10000000 kbit
[--- output truncated ---]

Now suppose that I wanted to further filter that output and include only the lines that contain the word Hardware. My inclination would be to add another pipe with another include, like this: sho int | inc Ethernet | inc Hardware. The problem is, this doesn’t work properly (if at all):

Arista-7280#sho int | inc Ethernet | inc Hardware
  Ethernet MTU 9214 bytes , BW 1000000 kbit
  Ethernet MTU 9214 bytes , BW 10000000 kbit
  Ethernet MTU 9214 bytes , BW 10000000 kbit
  Ethernet MTU 9214 bytes , BW 10000000 kbit
  Ethernet MTU 9214 bytes , BW 10000000 kbit
  Ethernet MTU 9214 bytes , BW 10000000 kbit
  Ethernet MTU 9214 bytes , BW 10000000 kbit

If I change my includes to greps, it works as I desire:

Arista-7280#sho int | grep Ethernet | grep Hardware
  Hardware is Ethernet, address is 001c.7390.93d0 (bia 001c.7390.93d0)
  Hardware is Ethernet, address is 001c.7390.93d1 (bia 001c.7390.93d1)
  Hardware is Ethernet, address is 001c.7390.93d2 (bia 001c.7390.93d2)
  Hardware is Ethernet, address is 001c.7390.93d3 (bia 001c.7390.93d3)
  Hardware is Ethernet, address is 001c.7390.93d4 (bia 001c.7390.93d4)
  Hardware is Ethernet, address is 001c.7390.93d5 (bia 001c.7390.93d5)
  Hardware is Ethernet, address is 001c.7390.93d6 (bia 001c.7390.93d6)
  Hardware is Ethernet, address is 001c.7390.93d7 (bia 001c.7390.93d7)

So why does this happen? Whereas include is part of the command-line interpreter, grep is a Linux command. Piping is a Linux function, so EOS behaves more like Linux when stacking Linux commands the way I have.

Note that you can also pipe to some Linux commands even though they’re not included in the help output. For example, egrep is not included in the output, but we can use it from the CLI:

Arista-7280(config)#sho int | egrep -i hardware
  Hardware is Ethernet, address is 001c.7390.93d0 (bia 001c.7390.93d0)
  Hardware is Ethernet, address is 001c.7390.93d1 (bia 001c.7390.93d1)
  Hardware is Ethernet, address is 001c.7390.93d2 (bia 001c.7390.93d2)
  Hardware is Ethernet, address is 001c.7390.93d3 (bia 001c.7390.93d3)
  Hardware is Ethernet, address is 001c.7390.93d4 (bia 001c.7390.93d4)
  Hardware is Ethernet, address is 001c.7390.93d5 (bia 001c.7390.93d5)

By the way, if you’re like me and have been forever frustrated by the inability to get a simple list of the Ethernet interface’s MAC addresses, check out this bit of Linux CLI/ Linux madness:

Arista(config)#show int | awk '/^[A-Z]/ {intf=$1} /, address is/{print intf, $6}'
Ethernet1 001c.7390.93d0
Ethernet2 001c.7390.93d1
Ethernet3 001c.7390.93d2
Ethernet4 001c.7390.93d3
Ethernet5 001c.7390.93d4
Ethernet6 001c.7390.93d5
[--output truncated--]

If you think that’s cool, save it as an alias:

Arista(config)#alias shmc show int | awk '/^[A-Z]/ {intf=$1} /, address
 is/{print intf, $6}'
Arista(config)#shmc
Ethernet1 001c.7390.93d0
Ethernet2 001c.7390.93d1
Ethernet3 001c.7390.93d2
Ethernet4 001c.7390.93d3
Ethernet5 001c.7390.93d4
Ethernet6 001c.7390.93d5
[--output truncated--]

Note that the alias command is one line and is wrapped in print to fit within the margins—it won’t work if you enter it as two lines.

EOS runs a flavor of Linux, and many of the command behaviors reflect that ancestry. For example, by default there is no pagination enabled in EOS when using the console. Therefore, when you execute the show run command, the output will scroll by until the entire running configuration has been displayed. To paginate on the fly, pipe your output to more. Just like using more in Linux, this will pause the output after the screen length (-1) has been met, at which point the prompt --more-- will be shown. At this point, user input is required to continue. Pressing Enter or Return will result in the advancement of a single line, whereas pressing the space bar will show another page. Pressing the letter q (or Q) or pressing Ctrl-C will break the output and return you to the command prompt:

Arista-7280#sho run | more
! Command: show running-config
! device: Arista-7280 (DCS-7280SE-72, EOS-4.16.6F.idboise)
!
! boot system flash:/EOS-4.16.6M.swi
!
alias conint sh interface | i connected
alias senz show interface counter error | nz
alias snz show interface counter | nz
alias spd show port-channel %1 detail all
alias sqnz show interface counter queue | nz
alias srnz show interface counter rate | nz
!
alias intdesc
   !! Usage: intdesc interface-name description
   10 config
   20 int %1
   30 desc %2
   40 exit
!
transceiver qsfp default-mode 4x10G
--More--

Speaking of show running-config, there’s a cool feature in EOS that will include all of the commands, even the defaults that aren’t usually shown. You do this by including the all keyword, and you can do it even when showing parts of the configuration such as an interface. Let me show you what I mean. Here’s the output from the command show run int e24:

Arista#sho run int e24
interface Ethernet24
   switchport access vlan 901
   switchport mode trunk

And here’s the output of the show run all int e24 command, truncated for brevity. All of the commands you see here are active; they’re just defaults, so they’re not usually shown:

Arista-7280#sho run all int e24
interface Ethernet24
   description [ MLAG Peer ]
   no shutdown
   default load-interval
   logging event link-status use-global
   no dcbx mode
   no mac-address
   no link-debounce
   no flowcontrol send
   no flowcontrol receive
   no mac timestamp
   no speed
   no l2 mtu
   default logging event congestion-drops
[-- output truncated --]

Another nice function that you can invoke while piping is the nz command. This outputs only lines that have values of nonzero. Let’s look at an example. Here, we have the output from the command show interfaces counters errors:

Arista-7280#sho int count error
Port        FCS    Align   Symbol       Rx    Runts   Giants        Tx
Et1           0        0        0        4        4        0         0
Et2           0        0        0        1        1        0         0
Et3          15        0        0       16        1        0         0
Et4          15        0        0       18        3        0         0
Et5           0        0        0        1        1        0         0
Et6           0        0        0        1        1        0         0
Et7           0        0        0        0        0        0         0
Et8          94        0        0       94        0        0         0
Et9           0        0        0        0        0        0         0
Et10          0        0        0        0        0        0         0
Et11          0        0        0        0        0        0         0
Et12          0        0        0        0        0        0         0
Et13          0        0        0        0        0        0         0
Et14          0        0        0        0        0        0         0
Et15          0        0        0        0        0        0         0
[-- output truncated --]

Many of the lines have values of all zeros. Chances are, we don’t care about this information, so why not display the same output without those lines? As here:

Arista-7280#sho interfaces counters errors | nz
Port        FCS    Align   Symbol       Rx    Runts   Giants        Tx
Et1           0        0        0        4        4        0         0
Et2           0        0        0        1        1        0         0
Et3          15        0        0       16        1        0         0
Et4          15        0        0       18        3        0         0
Et5           0        0        0        1        1        0         0
Et6           0        0        0        1        1        0         0
Et8          94        0        0       94        0        0         0
Et45          1        0        0        1        0        0         0

Notice that the lines that were all zero before are no longer included.

When I first started using Arista switches, I had been using Cisco Nexus switches for years, and the lack of the | last output modifier bugged me when using commands like show log. Then I sat and thought about what I knew about EOS and had a crazy idea. Remember earlier in this chapter when I showed how we could pipe to the Unix grep command? It struck me that grep was not listed as one of the options when piping:

Arista#sho run | ?
  LINE      Filter command by common Linux tools such as grep/awk/sed/wc
  append    Append redirected output to URL
  begin     Begin with the line that matches
  exclude   Exclude lines that match
  include   Include lines that match
  json      Produce JSON output for this command
  no-more   Disable pagination for this command
  nz        Include only non-zero counters
  redirect  Redirect output to URL
  section   Include sections that match
  tee       Copy output to URL

I reasoned that if I could pipe to one Unix command, I would likely be able to pipe to others. The Unix command that would serve me here is tail, so I cast caution to the wind and went for it with all the vigor of a sleep-deprived nerd hell-bent on discovery.

Here’s the output of the show log command piped through more:

Arista-7280#sho log | more
Syslog logging: enabled
    Buffer logging: level debugging
    Console logging: level errors
    Monitor logging: level errors
    Synchronous logging: disabled
    Trap logging: level informational
    Sequence numbers: disabled
    Syslog facility: local4
    Hostname format: Hostname only
    Repeat logging interval: disabled

Facility                   Severity            Effective Severity
--------------------       -------------       ------------------
aaa                        debugging           debugging
accounting                 debugging           debugging
acl                        debugging           debugging
agent                      debugging           debugging
ale                        debugging           debugging
arp                        debugging           debugging
bfd                        debugging           debugging
bgp                        debugging           debugging
capacity                   debugging           debugging
capi                       debugging           debugging
card                       debugging           debugging
clear                      debugging           debugging
cvx                        debugging           debugging
dataplane                  debugging           debugging
dot1x                      debugging           debugging
envmon                     debugging           debugging
eth                        debugging           debugging
eventmon                   debugging           debugging
 --More--

With bated breath, I entered my wicked conglomeration of EOS and Unix commands:

Arista-7280#sho log | tail
Sep 16 15:38:02 Arista-7280 Launcher: %LAUNCHER-6-PROCESS_START:
Configuring process 'FastClidHelper#2' to start in role
'AllSupervisors'
Sep 16 15:38:02 Arista-7280 Launcher: %LAUNCHER-6-PROCMGR_WARMSTART:
Initiating warm start of 'ProcMgr (worker)'
Sep 16 15:40:18 Arista-7280 Launcher: %LAUNCHER-6-PROCESS_STOP:
Configuring process 'FastClidHelper#2' to stop in role
'AllSupervisors'
Sep 16 15:40:18 Arista-7280 Launcher: %LAUNCHER-6-PROCMGR_WARMSTART:
Initiating warm start of 'ProcMgr (worker)'
Sep 16 15:43:05 Arista-7280 Cli: %SYS-5-CONFIG_I:
Configured from console by admin on con0 (0.0.0.0)
Sep 16 15:45:48 Arista-7280 Cli: %SYS-5-CONFIG_E: Enter
configuration mode from console by GAD on con0 (0.0.0.0)
Sep 16 15:48:33 Arista-7280 Rib: %OSPF-5-CONVERGED: OSPF in VRF
default has converged and its routes are in FIB
Sep 16 15:49:16 Arista-7280 Cli: %SYS-5-CONFIG_I: Configured from
console by GAD on con0 (0.0.0.0)
Sep 16 15:49:59 Arista-7280 Cli: %SYS-5-CONFIG_E: Enter configuration
 mode from console by GAD on con0 (0.0.0.0)
Sep 16 15:55:29 Arista-7280 Cli: %SYS-5-CONFIG_I: Configured from
console by GAD on con0 (0.0.0.0)

Holy crap! It worked! Such was my enthusiasm that my wife came into my home office at 2 a.m. and told me to go to bed, or at least keep it down. I suppose I should be lucky to have a wife, being that I’m a guy who finds the ability to mix EOS and Unix commands exciting.

As previously discussed, you can even stack Unix pipes:

Arista-7280#sho log | tail | grep GAD
Sep 16 15:45:48 Arista-7280 Cli: %SYS-5-CONFIG_E: Enter configuration mode from
 console by GAD
on con0 (0.0.0.0)
Sep 16 15:49:16 Arista-7280 Cli: %SYS-5-CONFIG_I: Configured from
console by GAD on con0 (0.0.0.0)
Sep 16 15:49:59 Arista-7280 Cli: %SYS-5-CONFIG_E: Enter configuration
mode from console by GAD on con0 (0.0.0.0)
Sep 16 15:55:29 Arista-7280 Cli: %SYS-5-CONFIG_I: Configured from
console by GAD on con0 (0.0.0.0)

Why stop at two? Now that my wife had left me to my late-night spell casting, I ventured down the rabbit hole. How about adding some redirection?

Arista-7280#sho log | tail | grep GAD > /mnt/flash/GAD.txt

Because tail is a Unix command, we must specify the full path to get to the flash drive. You’ll see what happens if you don’t in Chapter 12.

Now, my GAD.txt file is stored on the flash drive and can be seen with the dir command from EOS:

Arista-7280#dir
Directory of flash:/

       -rwx   436644679            May 17 00:44  EOS-4.16.6M.swi
       -rwx          27            Sep  6 23:27  boot-config
       drwx        4096            Sep  6 23:34  debug
       -rwx         424            Sep 16 16:09  gad.txt
       -rwx           0            Aug 23 06:07  no_ssd_var
       drwx        4096            Sep  6 23:33  persist
       drwx        4096            Aug 15 05:38  schedule
       -rwx        1635            Sep  6 23:31  startup-config
       -rwx           0            Sep  6 23:33  zerotouch-config

3547889664 bytes total (2658754560 bytes free)

Oh, when it comes to the log, there’s a nifty capability called show logging follow that shows real-time updates to the syslog from the CLI. I can’t really show that in a static book like this, but it behaves the same way as the tail –f filename command in Linux.

Lastly, there is a very cool option with show running-config that I really like. Have you ever wanted to see everything relating to Border Gateway Protocol (BGP)? Well, what if some of your BGP configuration isn’t part of the router BGP section? Check out this overly simplified BGP configuration example:

Arista-7280(config)#ip routing
Arista-7280(config)#router bgp 65001
Arista-7280(config-router-bgp)#neighbor 10.0.0.100 remote-as 65100
Arista-7280(config-router-bgp)#comment
Enter TEXT message. Type 'EOF' on its own line to end.
GAD's Rockin BGP config
EOF
Arista-7280(config-router-bgp)#int e1
Arista-7280(config-if-Et1)#description BGP uplink
Arista-7280(config-if-Et1)#exit
Arista-7280(config)#

If I wanted to get all of the BGP commands in one fell swoop, how would I do it? I know, let’s try piping to inc:

Arista-7280#sho run | inc bgp
router bgp 65001
Arista-7280#

Huh...well, that didn’t work. What about all those lines with BGP in them? Maybe we need to search for BGP in all caps?

Arista-7280#sho run | inc BGP
   description BGP uplink
   !! GAD's Rockin BGP config
Arista-7280#

Now I have the opposite problem where I got only the uppercase BGP matches! grep to the rescue, right? Nope.

Arista-7280#sho run | grep BGP
   description BGP uplink
   !! GAD's Rockin BGP config
Arista-7280#

Wait a sec. If I think like a Linux guy, I know that I can use the -i flag with grep in order to ignore case:

Arista-7280#sho run | grep -i BGP
   description BGP uplink
router bgp 65001
   !! GAD's Rockin BGP config
Arista-7280#

Hooray! No, wait...that’s not good enough, either. Look at the description line. It doesn’t show what interface that description is attached to. Luckily, EOS has a way to solve this problem using section. This works by using show running-config | section <regex>, where <regex> is a regular expression.

With this powerful command, check out the output we receive:

Arista-7280#sho run | section bgp
interface Ethernet1
   description BGP uplink
!
router bgp 65001
   !! GAD's Rockin BGP config
   neighbor 10.0.0.100 remote-as 65100
   neighbor 10.0.0.100 maximum-routes 12000
Arista-7280#

Beautiful! Not only does it show every line that matches bgp, but it matches regardless of case and includes the entire section in which that match was found. This is a fabulous tool, and after you become accustomed to using it, you’ll find that it’s damn hard to live without. When troubleshooting a feature like MLAG, the command show run | section mlag is a powerful tool!

Conclusion

Although EOS has obvious similarities to the industry-standard CLI, there are also clear improvements and changes that should make any seasoned networking veteran happy. Not only that, but remember that the entire OS was written from scratch to be something new, so regardless of how things look, what’s under the covers is arguably better than anything else out there.