ip helper-address

[alanchia2000]

Hi All,

Does ip helper-address work with 2 ip ranges in a VLAN in a catalyst 3750?

ip forward-protocol udp 6112

int vlan 1

ip address 192.168.0.1 255.255.255.0

int vlan 2

ip helper-address 192.168.0.100

ip address 192.168.1.100 255.255.255.0

ip address 192.168.2.100 255.255.255.0 secondary

[scottmac]

Normally, you need an "IP-Helper" command in the interface that is away from the resource you are trying to reach.

The broadcast request is received and if there's an IP-Helper established on that interface, the broadcast is passed toward that resource as a unicast ... so that it can pass through any other intermediate routers along the way.

Since you set that interface up as a "secondary," I believe it will work, since that interface is going to receive the broadcast request from either LAN (primary or secondary).

What I'm trying to figure out is why you are multi-netting ... it generally complicates things and is usually only used to accommodate transition from "the old address scheme" to "the new address scheme."

Are you short on ports?

Good Luck

Scott

Are you just short on ports?

[Richard Burts]

Scott

I am not clear what your concern is in answering the original question. VLAN 2 has a primary address, a secondary address, and a helper address. The helper address points to an address in the subnet of VLAN 1. So it seems to me to be pretty straightforward, any boradcast for one of the eligible protocols received on VLAN 2 will be forwarded to the address in VLAN 1.

HTH

Rick

[andrew.butterworth]

If your goal is to get DHCP working then you will not be able to allocate IP addresses from the 'secondary' IP network via the DHCP server unless you configure SuperScopes with both the networks in the superscope.

Wouldn't it be easier to create another VLAN?

Andy

[baileja]

Excellent choice my friend. Looks like your forwarding broadcasts for a game. Need for speed possibly? Or Diablo II? Your config looks good and should work providing this game only requires udp 6112 to locate the server and continous communication is unicast. Depending on the game, it may require broadcast communication back. Some games use TCP and UDP broadcast for location request and joining. Some use multicast for gameplay from server to client. So if your question is will your help-address statement work for both your primary and secondary addresses attached to vlan2, than yes.