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Webcast-Catalyst9k
New Member

HSRP OVER L3 ETHER CHANNEL

The l3 port channel config between 2 switches are follows

Sw1,

Interface range gig 1/19- 20

No switch port

Channel-group 12 mode desirable

Interface portchannel 21

Ip address 192.168.10.1

Sw2

Interface range gig 1/19- 20

No switch port

Channel-group 12 mode desirable

Interface portchannel 21

Ip address 192.168.10.1

The 192.168.10.0 is declared in OSPF.I have other layer 3 vlan 10, vlan 12, vlan 14 where I am enabling The HSRP on these interfaces.

Sw1 and sw2 are connected via L3 portchannel.

My question is will the HSRP advertisement pass over the L3 port channel.

Can we make it work so that HSRP adv goes via L3 port channel and functions good

7 REPLIES
Silver

Re: HSRP OVER L3 ETHER CHANNEL

i think it makes no sens to use hsrp and a layer3 link between the 2 switches.

hsrp traffic uses multicast as destination mac @, so there must be a layer 2 link for hsrp to reach neighbors (vlan in other switch)

New Member

Re: HSRP OVER L3 ETHER CHANNEL

if I enable IP PIM SPARSE MODE on the L3 port channel then will the HSRP groups start communicating over the L3

Hall of Fame Super Blue

Re: HSRP OVER L3 ETHER CHANNEL

Hi

No it won't because HSRP uses the address 224.0.0.2 and the 224.0.0.x multicast addresses have a ttl of 1 only ie. they are local only to their own subnet.

HTH

Jon

New Member

Re: HSRP OVER L3 ETHER CHANNEL

so if I increase the TTL from 1 to 3 of Multicast stream and if Enable ip pim sparse on both the switches then I guess HSRP packets wil be exchanged across

Hall of Fame Super Blue

Re: HSRP OVER L3 ETHER CHANNEL

Hi

You can't increase the ttl of 224.0.0.x addresses or have i misunderstood what you are asking ?

Jon

New Member

Re: HSRP OVER L3 ETHER CHANNEL

Please refer the attachment.You will see that Ten gig blade is connected between core 1 & 2 and runs ospf on /31 point- point .

There are gigabit ports 1 each on core 1 and 2 whic is enabled for layer 3 and has HSRP configured

please go thru and let me know if HSRP hello will be exchanged on Group 1 and group 2

between core 1 & 2 routers

Silver

Re: HSRP OVER L3 ETHER CHANNEL

if we speak about designing hsrp, in general it is supposed that one gateway could be either in core1 or core2. that means int vlan1 for example in core 1 and 2 have ip addresses in the same subnet.

now if you will connect core 1 and core 2 by a l3 connection, how can the 2 ip @ belong to same subnet ?

so i think you must have a l2 link between core 1 and 2

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