Nexus vPC | Routing over vPC

Let me tell you a sad story...
Some time ago, I ran into a problem. I was in the data centre all night and nearly pulled my hair out in frustration. No matter what I tried, I couldn't get vPC to work with #OSPF or #EIGRP
Let me save you this pain, and show you the pitfall of routing over #vPC, and how to avoid it, using layer-3 peer-router
This video is particularly helpful to network engineers working with vPC in production.
Also useful for CCNP Data Center, and CCIE Data Center
Part 1: How vPC Works - vPC adds redundancy to the data centre, while avoiding the older technologies like spanning-tree. See how it fits into your solution, and parts under the hood
• Nexus vPC | How vPC works
Part 2: vPC Configuration - Now you know how vPC works, you can start configuring. See how it's done by watching live config on real Nexus switches
• Nexus vPC | Configurat...
Part 3: Routing over vPC - Be careful! There are pitfalls when running routing protocols over vPC! I fell into one of these myself. See how you can avoid this
• Nexus vPC | Routing ov...
Some platforms now support hitless vPC role changes.
[networkdirecti...|Hitless vPC Role Change]
Read the full article at networkdirectio...
/ networkdirection
/ netwrkdirection
300-180 DCIT
300-160 DCID
300-165 DCII
layer3 peer-router

[@NetworkDirection]

Fore more info, see: networkdirection.net/vPC+and+Routing+Protocols

[@xeifora]

I love your storytelling combining with the real-time troubleshooting approach, that's really helped me a lot to understand the whole situation on how to apply dedicated command regarding your scenario. Great video !!

[@NetworkDirection]

Thank you , it's really good to hear that this video is providing practical help

[@ibrennan]

Excellent video, it took me weeks of research to fully understand what you explained in minutes. I have a similar project where we were having issues with EIGRP, "layer3 peer-router" fixed it!

[@NetworkDirection]

Took me weeks too 🤓 I went through a lot of pain along the way

[@kellymoses8566]

This issue is fundamentally caused by the fact that vPC makes two switches look like one device at layer 2 but NOT at layer 3.

[@francescogalli4033]

Really loved it That is exactly what I've experienced last week after an upgrade to nxos 7.3.7 with eigrp Lucky me, i remembered your video Thanks

[@NetworkDirection]

Really glad that I saved you the trouble I had!

[@MrTetinho23]

what was the prev version ? why did you have such a problem after the upgrade?

[@chetanpadshala18111991]

That is really good information on Routing Over VPC. Short, Simple and Amazing information. Thank you.

[@NetworkDirection]

Thanks Chetan, There’s definitely a few gotchas to be aware of. I hope the video helps clear them up

[@shawn_8888]

Thx a lot for sharing your issue, will keep note of this.

[@rajpjunior]

heheh I like how it begins. "Oh, the horror!!! Routing and vPC!!!!!" :-D

[@CiscoPhipse]

Thanks 👍 You kept us waiting a while for this video 🙂

[@NetworkDirection]

+Euan Phipps I sure did! I had to learn a few new video tricks. I hope it was worth the wait 😃

[@motiamiful]

does this solution of applying the 'layer3 peer-router' command is suitable for multicast traffic as well? BTW - great video great explanations!

[@NetworkDirection]

As far as I'm aware, yes, this is supported with multicast as well. I haven't had any issues myself. This could vary depending on the platform. The Nexus range is a bit special like that. Something that's fine on an N3K may not work on an N9K. I would recommend asking TAC what they support, just to be sure. If you do learn anything of interest along the way, I encourage you to share it here. It's always nice to learn something new :)

[@AH-ps3uv]

So in summary from what i have understood: it is the purpose that the router forms a neighborship with only one of the NX-OS devices that are bundled in the VPC domain. even thought both the NX-OS devices act as 1 device It can happen that the router sends IGP related data to the other NX-OS device ( because of the LAG hashing algortihm) With the peer-router command configured on the NX-OS devices this is no problem because the NX-OS device that receives the IGP related data which was not ment for him , he will send it over the peer-link to the other NX-OS device. But the problem is that he will decrement the TTL which in many times with IGPs is 1 (so it will become 0 and hence discarded), so the NX-OS device for which the IGP related data was ment never receives it. result = IGP neighborship flapping solution: add layer3 peer-router command or increase the IGP ttl to 2. does this describe the issue correctly?

[@NetworkDirection]

That's pretty close. However, remember that vPC is a layer-2 technology, while routing is L3. The pair acts as a single device from a layer-2 perspective From layer-3, each device acts independantly

[@Soundwave-F7Z]

thanks for the video. we have a pair of vpc 9ks that we're attempting to do BGP neighborship with an active/standby ASA so they can excahange routes. Do you recommend we that we use the same AS on both the 9ks or different AS numbers?

[@OkaKeanu]

Thanks , How configuration EBGP from VPC to VSS switch , should we use L2 link or L3 link ?should we have additional link between vpc switch ?

[@NetworkDirection]

Using Layer 3 routed ports is preferred for peering. eBGP can use multi hop anyway, so you shouldn’t have the same problems that IGPs have

[@ualperkus]

Thank you. Very good video.

[@musalyh]

4:20 sw2 and router connected interfaces are different networks?? As far as I know, the TTL is not reduced for the same network. Therefore, if it is the same network, the TTL will not be 0, so I don't think there is a problem with OSPF. What do you think in my opinion?

[@NetworkDirection]

I think TTL would only be reduced for a L3 hop, so you're right. If they're in the same L3 network, the TTL will not be reduced

[@mauricewalker2350]

So the big question on everybody's mind is if I add the layer3 peer router command to both switches will traffic be interrupted? I have this exact issue with my edge switch and I'd like to fix it during a maintenance window but I need to tell my business if there's going to be a possible downtime. Thx.

[@NetworkDirection]

That's a good question... I don't remember for sure, but I don't think it causes any downtime. I recommend calling TAC to check with them

[@mauricewalker2350]

@@NetworkDirection I went ahead and did this during a maintenance window and no downtime was experienced. I also had a colleague at another company confirm in his test lab. Appreciate this video very much and my network is running much smoother because of it.

[@NetworkDirection]

@@mauricewalker2350 Glad to hear it went well for you, and thanks for sharing your experience here

[@headdstrong983]

Thanks for video.How do i announce my subnet in ospf in nx-os.For example: in isr router press command network 10.1.1.0 0.0.0.255 area 1 But in nexus not found this command

[@NetworkDirection]

Nexus is a bit different. From memory, it's configured under the interface

[@martsiro]

wowww cool solution thks a lot

[@moorthyy27]

good videos thanks

[@NetworkDirection]

Thanks Moorthy!

[@junnairmanla4928]

Thanks for this!

[@NetworkDirection]

Thanks for the feedback! I was thinking of maybe doing some VxLAN stuff next. How does that sound?

[@junnairmanla4928]

Network Direction that would be very informative! Looking forward to that!

[@alihabib3201]

Could you please share the full config of the topology

[@Emerb9]

These videos are everything. I have to connect two 5k (5548, 5596) to a Nexus 2k in the morning. From your video's can I connect the 2k to Vlan 20?

[@NetworkDirection]

That's a bit different to this video... It depends on the topology that you want to achieve. Have a look here: www.cisco.com/c/en/us/support/docs/switches/nexus-2000-series-fabric-extenders/200363-nexus-2000-fabric-extenders-supported-un.html

[@Emerb9]

Network Direction Thank you! I will check the document out. I will more than likely run EIGRP.

[@NetworkDirection]

You’re welcome! As for EIGRP, it will depend on what’s peering with what. Are you attaching a router to the FEX?

[@Emerb9]

No, I will not have a router. I will have two servers hanging off the 2k in separate vlans. The goal is to setup up active/active between the 5k’s and test inter vlan connectivity. This goal was assigned to me this today.

[@Emerb9]

Network Direction similar to your nexus vpc video one, instead of having two servers connecting to the 5k’s (via vpc) I will have a 2k and the two serves connected to the 2k.

[@harshadavirle8632]

Nice sir.

[@NetworkDirection]

Thanks!

[@farzananadaf1518]

So confusing this third part

[@NetworkDirection]

It's true, there's a lot in it. I learned the hard way.

[@CanyonSteve-z8j]

This is what you came to see - kzbin.info/www/bejne/gYHWn3xsnZaFf9U