In Part 1 we set the stage and configure the FTD to BGP (w/ GR enabled) with the N9K.

In part two it is now time to play! 🙂

What Will be Covered in Part 2

Basically I’m going to

• Grab a sniffer trace of the BGP coming up – to show GR in capabilities being sent from the FTD
• Start pinging from Airlines23 to 14.0.0.114
• Cause failover by going into FMC and switching active FTD
• Look at results (spoiler: it’s all going to be beautiful).

BGP Starting Up

When two devices BGP neighbor they send “capabilities” to each other. In Part 1 you saw at the end of the blog the results of show ip bgp neighbor 21.0.0.1 as seen in Airlines24 and the fact that Airlines24 had listed what the FTD was advertising as far as the BGP capabilities configured in the FTD for that BGP neighbor.

Below is an example of what you would see if you had done of sniffer trace of the BGP startup.

Quick and Simple Show and Tell

• Start ping from Airlines23 to 14.0.0.114 (interval 1 sec, count unlimited)
• Switch Active/Standby on the FTDs
• Quickly look at Airlines24 while 11.0.0.0/24 is still “stale” but being used.
• Results of ping

Start the Ping

Okay truth? lol. This is the entire ping. With no loss at all. I started the ping and then went RIGHT to the FMC and switched the active/standby FTDs. So this is the start of the ping and also the ping results. :).

So honestly… how are we REALLY to know that anything truly even happened? I mean… no loss. Seriously… the skeptic in all of us would be like… come on… you are pulling my leg…. you didn’t fail ANYTHING!

Well let’s see what Airlines24 thinks happened.

Airlines24’s View of 11.0.0.0/24

The above is Airlines24’s view of the prefix 11.0.0.0/24 as advertised to it by the FTD. This is “normal”. Gotta be pretty quick to catch it “stale” and with the BGP GR timers invoked. I missed it a few times but finally caught it. 🙂

“Stale time” is a Graceful restart parameter. So basically we can tell by this that Airlines24 kicked into GR mindset and set the 11.0.0.0/24 prefix into “stale”. Where can you find what the default GR parameters are since we didn’t specify any. Let’s go back to Airlines24 and look in show ip bgp neighbor 21.0.0.1 and go to the graceful restart parameters section

Yup that is it. BGP GR is simple to config and works great!

🙂

NOTE: For more information about BGP Graceful Restart I suggest this link

https://www.cisco.com/en/US/docs/ios/12_2t/12_2t15/feature/guide/ftbgpnsf.html#wp1041499