VRRP v2 vs VRRP v3 // dscp cs6 vs dscp cs0 ??

[Yassine Haida]

Hello guys,

I work for French ISP . I worked on the VRRPv 3 protocol more precisely on the dscp fields of this protocol. (I use an ipv4 address plan)

I noticed that the dscp field in VRRP v2 is CS6 which is normal. My question is the following. Why in VRRP v3 the DSCP field is CS0?

I know that version 3 was made for the arrival of ipv6. vrrp V3 can be V2 compatible (announcement in v2 and announcement in V3 to the backup router)

Even when using V2 compatibility, the dscp Field remains at CS0.

The problem that the following, in case of congestion of the client LAN, it is possible that the VRRP announcements is dropped because they are marked in CS0.

what is the best method? should we go back to VRRP V2? rather use HSRP? mark vrrp packets ??

thank  you for  your help..!!

[Yassine Haida]

Nobody to answer my questions? I think it’s a bug. I have tried different routers with different iOS versions and I always notice the same problem. In vrrpv3 with ipv4 the dscp field is cs0. it should be cs6. I've tried this protocol with another manufacturer and I do not see this problem. I would like to have the answer of a cisco expert on this subject. Thanks in advance for your answer

[adil.haida]

Hello,

after the lab testing.

this is clear for me There is a "BUG" Cisco has to work on the subject.
when you work  with fhrp version vrrp v3 and

with the interface vlan or the physical interface configured with

this command applied " vrrp 91 address-family ipv4"

the dscp value of the vrrp packet  is not CS6  but "strangly" CS0 .

 when the traffic is very high  and the qos is working .

the vrrp packets are dropped  and the backup  router becom the master .

we are faced off two master vrrp router on the network . (This is split-brain scenario)

I find for that a workround.  you have to match multicast vrrp ip and set the correct value of the dscp .

on others company like HPE or Extreme Networks or huawei.

natively  the  dscp filed is  cs6  or on CS7 the maximum priority of traffic

if you need more details you can contact: me adil.haida@free.fr

i think all ios router version are concerned

i  checked on cisco bug tool  but nothing talk about this problem.

[hk_net]

sorry to state the obvious but I guess you should raise this issue with cisco TAC.