tpat
asked on
Cisco GLBP Doubt
I have a doubt with glbp
In the figure that i have attached,
let's assume that the client1 issued an arp broadcast request, so the switch will have the source mac add of client1 in the mac address table and the port no , the avg will send an arp reply with the virtual mac address and the switch will record the virtual mac and the port no of the source, which in this case is the virtual mac address of Router A.
i found no doubt in the above but,
when the client2 issues an arp, the avg(RA) will receive it and will send the virtual mac address of the avf(Router B), so now the swich will record the mac address of the sender which in this case is virtual mac addr of Router B (but given by Router A), so In the switch cam table, mac addr will be the virtual mac addr of routerb, but the port no recorded by the switch would be that of the port on which the routerA is present as it was the replier to the arp query,
So how does a switch know that it has to forward the frames to routerB as the replier to the arp query fro client B was Router A and its port is recorded by the switch.
GLBP.png
In the figure that i have attached,
let's assume that the client1 issued an arp broadcast request, so the switch will have the source mac add of client1 in the mac address table and the port no , the avg will send an arp reply with the virtual mac address and the switch will record the virtual mac and the port no of the source, which in this case is the virtual mac address of Router A.
i found no doubt in the above but,
when the client2 issues an arp, the avg(RA) will receive it and will send the virtual mac address of the avf(Router B), so now the swich will record the mac address of the sender which in this case is virtual mac addr of Router B (but given by Router A), so In the switch cam table, mac addr will be the virtual mac addr of routerb, but the port no recorded by the switch would be that of the port on which the routerA is present as it was the replier to the arp query,
So how does a switch know that it has to forward the frames to routerB as the replier to the arp query fro client B was Router A and its port is recorded by the switch.
GLBP.png
ASKER
So what would be the layer 2 information in the ARP Reply from router a to client b.
would it be:
SMAC: 0007.b400.0101
DMAC: client B's mac address.
ARP REPLY:
SMAC: 0007.b400.0102
DMAC: client 2's mac address
SIP: 10.21.8.10
DIP: client 2's ip address
would it be:
SMAC: 0007.b400.0101
DMAC: client B's mac address.
ARP REPLY:
SMAC: 0007.b400.0102
DMAC: client 2's mac address
SIP: 10.21.8.10
DIP: client 2's ip address
ASKER CERTIFIED SOLUTION
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
SOLUTION
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
ASKER
So the trace shows the ARP reply has the Source Mac address of the physical interface of the router, and the ARP payload has the source mac adress as the virtual mac address. Am i right?
>Am i right?
correct, no different that what was discussed prior
correct, no different that what was discussed prior
your correct.
ASKER
Understood it!
The ARP reply information for the destination MAC and IP (Router B) is contained in the data payload of the Ethernet fram (ARP data is encapsulated into an Ethernet frame) and not in the source and destination of the Ethernet Frame as you think it is, these are 2 different pieces of information.
http://book.chinaunix.net/special/ebook/oreilly/Understanding_Linux_Network_Internals/0596002556/understandlni-CHP-28-SECT-1.html
Billy