ELRP across multiple stacks

[Anonymous]

Hi,

Have a scenario where we are using ELRP, which works great for disabling ports on the same stack but we have a stack in the same room and want to protect across the two - is this possible?

My theory was that should an edge port see a ELRP PDU from the other stack, due to ELRP also being enabled on the other edge port it should disable?

Originally I didn't have port 1:52 on stacks (uplink to cores) included in any of the ELRP config, but added it in trying to get it to work across stacks.

#### Stack A ELRP config, port 1:52 is a lag to core hence it being excluded:

enable elrp-client
configure elrp-client periodic B20_23-L-GND-MGMT ports 1:45-48,1:52,2:45-48,3:45-48,4:45-48 interval 1 log-and-trap disable-port ingress permanent
configure elrp-client periodic B20_23-L-GND-Data ports 1:1-40,1:52,2:1-40,3:1-40,4:1-40 interval 1 log-and-trap disable-port ingress permanent
configure elrp-client periodic B20_23-L-GND-Voice ports 1:1-40,1:52,2:1-40,3:1-40,4:1-40 interval 1 log-and-trap disable-port ingress permanent
configure elrp-client periodic B20_23-L-GND-Printers ports 1:41-44,1:52,2:41-44,3:41-44,4:41-44 interval 1 log-and-trap disable-port ingress permanent
configure elrp-client disable-port exclude 1:52

##### Stack B ELRP config, port 1:52 is a lag to core hence it being excluded:

enable elrp-client
configure elrp-client periodic B20_23-GND-MGMT ports 1:45-48,1:52,2:45-48,3:45-48,4:45-48 interval 1 log-and-trap disable-port ingress permanent
configure elrp-client periodic B20_23-GND-Data ports 1:1-40,1:52,2:1-40,3:1-40,4:1-40 interval 1 log-and-trap disable-port ingress permanent
configure elrp-client periodic B20_23-GND-Voice ports 1:1-40,1:52,2:1-40,3:1-40,4:1-40 interval 1 log-and-trap disable-port ingress permanent
configure elrp-client periodic B20_23-GND-Printers ports 1:41-44,1:52,2:41-44,3:41-44,4:41-44 interval 1 log-and-trap disable-port ingress permanent
configure elrp-client disable-port exclude 1:52

##### Core A ELRP config. Originally I had no ELRP config on the core but added in trying to get to work. Ports 1 & 2 go to stacks:

enable elrp-client
configure elrp-client periodic B20_23-L-GND-Data ports 1 interval 1 log-and-trap disable-port ingress permanent
configure elrp-client periodic B20_23-GND-Data ports 2 interval 1 log-and-trap disable-port ingress permanent
configure elrp-client periodic B20_23-L-GND-Voice ports 1 interval 1 log-and-trap disable-port ingress permanent
configure elrp-client periodic B20_23-GND-Voice ports 2 interval 1 log-and-trap disable-port ingress permanent
configure elrp-client periodic B20_23-L-GND-Printers ports 1 interval 1 log-and-trap disable-port ingress permanent
configure elrp-client periodic B20_23-GND-Printers ports 2 interval 1 log-and-trap disable-port ingress permanent
configure elrp-client periodic B20_23-L-GND-MGMT ports 1 interval 1 log-and-trap disable-port ingress permanent
configure elrp-client periodic B20_23-GND-MGMT ports 2 interval 1 log-and-trap disable-port ingress permanent
configure elrp-client disable-port exclude 1
configure elrp-client disable-port exclude 2

##### Core A ELRP config. Originally I had no ELRP config on the core but added in trying to get to work: Ports 1 & 2 go to stacks:

enable elrp-client
configure elrp-client periodic B20_23-L-GND-Data ports 1 interval 1 log-and-trap disable-port ingress permanent
configure elrp-client periodic B20_23-GND-Data ports 2 interval 1 log-and-trap disable-port ingress permanent
configure elrp-client periodic B20_23-L-GND-Voice ports 1 interval 1 log-and-trap disable-port ingress permanent
configure elrp-client periodic B20_23-GND-Voice ports 2 interval 1 log-and-trap disable-port ingress permanent
configure elrp-client periodic B20_23-L-GND-Printers ports 1 interval 1 log-and-trap disable-port ingress permanent
configure elrp-client periodic B20_23-GND-Printers ports 2 interval 1 log-and-trap disable-port ingress permanent
configure elrp-client periodic B20_23-L-GND-MGMT ports 1 interval 1 log-and-trap disable-port ingress permanent
configure elrp-client periodic B20_23-GND-MGMT ports 2 interval 1 log-and-trap disable-port ingress permanent
configure elrp-client disable-port exclude 1
configure elrp-client disable-port exclude 2

Many thanks in advance

[Anonymous]

Hi Stephane,

Thanks for posting.

The config above isn't working. Originally I didn't have any ELRP config on the core, I'm not sure I really need that anyway - just at the edge, so long as I include the uplinks on the edge stacks?

With it not working and essentially using multicast, would I perhaps need to enable ipmc forwarding for all the VLANs on both the cores to get it working - which obviously wouldn't be a good idea, but perhaps something along those lines?

https://gtacknowledge.extremenetworks.com/articles/How_To/How-To-Pass-Multicast-Traffic-on-an-Extrem...

Thanks

[Stephane_Grosj1]

Hi,

The ELRP PDU is a multicast frame, so it would flow through the uplink without you needed to configure it. If you create a loop between two stacks, that loop will be detected as the ELRP PDU will be seen back from the uplink. Then ELRP would disable one port, based on your config. You don't want the uplink to be disabled, of course, so exclude it.