HSRP and DHCP

[The_guroo_2]

Guys we have two  WAN routers which is running HSRP on the LAN..........one is active and on eis standby......the issue is that i have to config DHCPon the router??? how will i achieve that ....what if if one router dies i am confused

Can someone explain

[Reza Sharifi]

I am not sure what is the confusion here. HSRP is configured on the physical interface, but DHCP helper address is on the vlan (SVI) interface.

HTH

[The_guroo_2]

Hi

The two routers have biulin swicthing module i have config vlan 10 at both end 192.168.1.2/24 and on the other swicthing mocule 192.168.1.3/24. The HSRP address is 192.168.1.1/24

now i have to config DHCP pool from 192.168.1.0/24 network excluding first three IPS.....my question is that shd i config it on both routers or just one if one then what if it dies and if two how i will avoid duplications

Did you get the point

[Reza Sharifi]

Yes, you need to configure the ip helper address in both router's SVI interfaces.  You also need to configure the pool for both routers with default route pointing to the HSRP virtual IP (192.168.1.1/24).  In this case if one of the routers fails, you can get IP address from the stand-by.

What type of switch module and router do you have?

HTH

[Eduardo Aliaga]

Hi. Cisco doesn't support stateful redundant DHCP servers, so the DHCP routers won't synchronize their DHCP lease tables. Both DHCP servers will work independently and will have to rely on pings to avoid DHCP conflicts, which is not a perfect way to avoid conflicts.

So it's recommended to use a little trick. You have to configure DHCP exactly the same on both routers with the only exception of the DHCP Pool. Youl will have to divide the DHCP pool in two, and assign the first half of the pool to one of the routers and the second half of the pool to the second router.

Or you could use a DHCP server which does support stateful redundancy like free Linux ISC dhcpd.