HSRP Issue over OTV

[datamodule]

We have following design

DC1 -- cisco 3750 switch ----- Nexus 7K(2 Nexus switches with vPC) ---- OTV --- Cloud --- DC2 -- OTV(2 Cisco ASR1K)---- Cisco 6500 (2 cisco 6500 switches no VSS) --- cisco 3750 switch

The two cisco 3750 switches are having some vlans configured with HSRP and when i checked sh standby vlan 10 it show active on both switches instead of one showing standby.

Output shows=Standby router is unknown

I am able to ping SVI's from each switch without any issue.

THanks for your help

[Rajeshkumar Gatti · Accepted solution]

Hi,

You may have HSRP isolation configs on the OTV VDC which could be causing this behavior. It is a recommended config when deploying OTV to have HSRP localized to each datacenter so one does not have to traverse the OTV overlay for any routing.

A sample config for 7k is below for reference on how FHRP (HSRP orany other similar protocols) isolation

http://www.cisco.com/c/en/us/products/collateral/switches/nexus-7000-series-switches/white_paper_c11-644634.html#_Toc408469214

-Raj

[datamodule]

Raj,

Thanks for your reply.Yes i can see in my config on OTV VDC there is HSRP localized config.How to test for one vlan to see if that is causing the issue.From the following list how to remove one vlan or what is the solution.

vlan filter HSRP_Localization vlan-list 8,10,12

Regards

[Rajeshkumar Gatti]

Its going to be a bit tricky to do only one vlan as there are 3 things that are part of the HSRP localization on 7k

1. VACL as you have listed
vlan filter HSRP_Localization vlan-list <OTV_Extended_VLANs>

2. ARP suppression (not sure if you have this)
ip arp inspection filter HSRP_VMAC_ARP <OTV_Extended_VLANs>


3. MAC advertisement filtering (not sure if you have this)
otv-isis default
  vpn Overlay0
    redistribute filter route-map OTV_HSRP_filter

If you tweak item 1 by removing the filter for vlan X then you will see HSRP states to be good but mac advertisement will not be correct.
I would not recommend doing this for production vlans.
I would recommend you to remove all the HSRP localization configs and that too during a change window since traffic routing will change.

Use this doc to better understand FHRP isolation and its configs
http://www.cisco.com/c/en/us/td/docs/solutions/Enterprise/Data_Center/DCI/whitepaper/DCI3_OTV_Intro/DCI_1.html#wp1220161

-Raj