I just wanted to ask you about HSRP interoperating with non-Cisco switches.
I got two Cisco 2800s with four different interfaces (3x FastEth, 1x ISDN).
HSRP will be configured for three of them (the fourth is an ISDN connection, and as far as I know, HSRP does not work with ISDN interfaces).
Well, the both routers will be connected in each network to a non-cisco switch (i proposed Catalyst, but the Boss said it had to be with unmanaged D-Link).......
My question is:
- HSRP uses a well-known MAC address for identify the interfaces.
- The switch will register this MAC address in the MAC-Table for each router. It means that he active link will have the well-known HSRP-MAC address.
- What will happen if the router fails? After all, the HSRP-MAC address will still be in the Forwarding Table of the switch, right?
- Will it not be a problem for the switch this issue?
- Which solution do I have? The switch is non-managed......
Thanks a lot! ;-)
what Simon is saying is that when an HSRP switchover happens the new active device will send out a Gratuitous ARP.
The frame has a destination of broadcast and a MAC source = HSRP VIP MAC addres.
in this way switches CAM tables are updated.
This should work even with unmanaged switches like the ones you have to use.
Actually without that gratuitous ARP HSRP would be of no use with any type of LAN switches it is a needed step.
PCs ARP tables are not affected by this message because it restates known information
Hope to help
- If R1 is the active router (and R2 the Standby), the 0000.0c07.acXX address will be linked to the Port 3 - Yes
- If PC1 or PC2 try to communicate the outer world, will jump over R1 - Yes
- If R1 fails, the 0000.0c07.acXX address will still be linked to the Port 3 of the switch, right - No depoends on the below.
- When R2 activates, the switch will have the address 0000.0c07.acXX in Port 3 as well as Port 4. Am I right - R2 will send an ARP Broadcast, the switch should re-write it's cam/mac address table pointing the virutal mac address to port 4
- What happens then if PC1 or PC2 try to reach t he outer world? - if the above step is OK, there will be no issues
- When I say that the switch is unmanaged is that it has no menus or confugration options. That means I cannot change agings - Should not make a great deal of difference, what modle is the switch>
You will have a problem as when the standby router takes over from the active then it sends a gratuitius ARP which then changes the MAC table on the switch and also changes the ARP table on the devices.
This link is good at understanding the process, if you scroll down a bit you can see that a 'I' action happens when and 'Event 3' happens.