Router acting as DHCP server, need to add 2nd cable for redundancy.

[Andrew White]

Hello,

We have a typical L3/L2 campus network.  We have 2 core L3 switches and 8 L2 switches that trunk to both cores.  Off one core we have a router which is our DHCP server for all our VLANs.  It's IP is 192.168.21.1/24 and it's gateway is 192.168.21.254/24 which is the VLAN 21 (HSRP) on the 2 cores.

I want to add a second cable to the DHCP router and add it to the other core for redundancy, I can't put it in the same subnet, is it best I just put it in another vlan the L2 switch can get to?

I think at some point we can get a server where we can give both nics the same virtual IP and bundle them.

Thanks

[Reza Sharifi]

Hi,

If the router supports Portchannel, you can put both connections in one Portchannel and use the same IP (192.168.21.1/24) for both links.

HTH

[Andrew White]

All these years I didn't know a router could do that, I have don't many a tim eon switches.  I've configured it like this, but can't ping 192.168.21.1 from the cores yet.

interface Port-channel1
 ip address 192.168.21.1 255.255.255.0
 hold-queue 150 in
!
interface FastEthernet0/0
 no ip address
 duplex auto
 speed auto
 channel-group 1
!
interface FastEthernet0/1
 no ip address
 duplex auto
 speed auto
 channel-group 1

ip route 0.0.0.0 0.0.0.0 192.168.21.254

192.168.21.254 is the HSRP address the 2 cores are using.

[Reza Sharifi]

Can you post the config from the switches?