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Bronze

few questions about gateway load balancing protocol

Hi every body!

i have few questions about GLBP

1) How many routers at maximum can load balance the traffic in GLBP group including active virtual gateway?

2) If there are 6 routers, r1,r2,r3,r4,r5 and r6.

r1 has priority 200,r2 has 199,r3 has 198,r4 has 197,and r6 has 196. ( here priority means GLBP priority)

r1 would be elected as active virtual gateway. which will be selected as active virtual forwarders ?

3)What is GLBP peer? does it include only active virtual gateway and active virtual forwarders? or it also include those routers which are not active virtual forwarder but are backup routers?

4)Do only active virtual gateway and active virtual forwarders exchanges hellos? or back up routers also exchanges hellos?

5) do timers on active virtual gateway overwrite the timers value on active virtual forwarders?

Thanks a lot and have a nice weekend!

4 REPLIES
Hall of Fame Super Bronze

Re: few questions about gateway load balancing protocol

which will be selected as active virtual forwarders ?

All the routers in the GLBP group will be AVFs.

AVG assigns each router (including itself) a virtual MAC in order for them to reply ARP requests...

3)What is GLBP peer?

Routers with GLBP enabled participating in the same GLBP group.

does it include only active virtual gateway and active virtual forwarders?

All routers, see above.

or it also include those routers which are not active virtual forwarder but are backup routers?

There isn't a concept of backup in GLBP, all routers are forwarding traffic.

4)Do only active virtual gateway and active virtual forwarders exchanges hellos? or back up routers also exchanges hellos?

Again, no backup router concept in GLBP. GLBP members communicate between each other through hello messages sent every 3 seconds to the multicast address 224.0.0.102, User Datagram Protocol (UDP) port 3222 (source and destination).

http://www.cisco.com/en/US/docs/ios/ipapp/configuration/guide/ipapp_glbp_ps6350_TSD_Products_Configuration_Guide_Chapter.html

5) do timers on active virtual gateway overwrite the timers value on active virtual forwarders?

Yes.

http://www.cisco.com/en/US/docs/ios/ha/command/reference/ha_f1.html#wp1032645

Bronze

Re: few questions about gateway load balancing protocol

Hi Edison!

Let me quote from my book

" The AVG (active virtual gateway) also assigns the necessary virtual mac addresses to each of the routers participating in GLBP group. Upto four virtual Mac addresses can be used in any group. each of these routers is refered to as an active virtual forwarded(AvF),forwarding traffic received on its virtual mac address. other routers in the group serve as backup or secondary virtual forwarders,in case AVF fails"

pg # 331,chap # 13, title CCNP BCMSN official exam certification guide by David Hucaby.

Thanks a lot!

Bronze

Re: few questions about gateway load balancing protocol

I find another link which contradicts the cisco link you forwarded to me as well.

http://tcpmag.com/qanda/article.asp?editorialsid=308

According to the Cisco link, only AVG and standby virtual gateway load balance the traffic while others stay in listening state.

But according to the book and above link, up to four routers also knows as AVF load balance the traffic while the others , also known as secondary AVF, stay in listening state. Secondary AVF listen to group' messages.

Do these Secondary avf only listen or they send their hellos to AVG like AVFs routers?

thanks a lot!

Hall of Fame Super Bronze

Re: few questions about gateway load balancing protocol

Sarah,

Good information regarding the limitation. It's odd that's not published on the link I provided. I have to do more digging on Monday to find out if the limitation is still in effect.

My understanding is that all routers participating in the GLBP group with load share the traffic and in reality they are all AVFs servicing the LAN segment they are attached to.

__

Edison.

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