VRRP on loopback

[netmask127]

Hi,

So I'm trying to configure VRRP on two CISCO 3850s (not stacked), so far I have it working with a VLAN interface. But the problem I see is that the VLAN interface only comes online when a host is connected to it. So without a host the VRRP interface is also down. This prevents other hosts from other VLANs from using the VRRP interface.

Does anyone know a way to configure a VRRP interface that is always up? Like on a loopback interface.

[Mark Malone]

Hi

That would defeat the purpose of the feature how would it then know to failover if its always up/up ?

use physical interfaces or have multiple SVI interfaces instead of just 1 vlan

[netmask127]

Hi Mark,

I didn't word that question very well...I meant I would like the VRRP virtual interface to be reachable without being reliant on the VLAN being up. So for example I have VLAN2 on both switches connected via a trunk and have VRRP IP 192.168.0.1. There is VLAN3 on one of the switches with host X that uses 192.168.0.1 as a gateway. I boot the switches up and there's no hosts on VLAN2 (i.e hosts on VLAN2 are not started yet), VRRP 192.168.0.1 is down because VLAN2 is down. So now host X cannot ping 192.168.0.1, but the switch is up. This scenario may not be realistic but with the constraints I have on this setup it can happen. For multicast routing with PIM it's possible to set a loopback interface as the RP, I'm just thinking if there's something similar with VRRP.

Are you saying I need to enable VRRP to more VLANs and routing ports? So for the above example I would add VRRP IP 192.168.0.1 to VLAN3 as well? And if I extrapolate this I would have VRRP on all routing ports and VLANs so that the behaviour is what I wanted (i.e VRRP IP is reachable as long as the switches are up).

[Mark Malone]

Hi so first getting a vlan to come up is there is a couple of methods it doesn't just have to be an access port once there is a valid stp instance it will come up too , my mgmt. vlan is spread across the globe with no access ports associated with it but if you using this for failover reasons usually there would be hosts or servers in play too

1. VLAN configured on that interface, either as an access port or trunk port
2. that interface is in STP forwarding mode for that VLAN

i would have the VRRP on each vlan that would be standard in real world and then you can track and upstream route or physical interface in conjunction with it so when the route/interface becomes unreachable you can automatically fail over to the second switch , you would use ip sla with this, that's a real world common scenario and is documented below using HSRP but its same thing with each FHRP same setup VRRP just to show you

http://www.cisco.com/c/en/us/td/docs/switches/blades/3040/software/release/12-2_44_se/configuration/guide/swhsrp.html

http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipapp/configuration/12-4/iap-12-4-book/iap-eot.html#GUID-EEC74523-8A92-445F-BE87-A0CD3B00A889