From: Jonathan Hays (nomad@gfoyle.org)
Date: Mon Jan 12 2004 - 09:37:33 GMT-3
comments inline:
>Hi group,
>
>On same subnet, I have two routers act as DHCP relay agents
>with command "ip helper-address" pointing to different
>external DHCP servers. In case the client broadcast the DHCP
>request packets and both two routers will redirect the packets
>to DHCP servers. DHCP servers will reply to the relay agents
>respectively. I have the following queries:
>1) Will the DHCP client reject one of the returned DHCP reply.
#####
DHCP client will lease from the first DHCP server it hears, and ignore
any additional ones.
>2) In subsequent DHCP renew process, are there any conflict
>exist since both DHCP relay agent will redirect the renew
>request to different DHCP servers. But only one should renew
>the IP address, the other one should reject, am I correct?
#####
When the DHCP client renews its lease the relay agent is not involved
since this is a unicast exchange directly to the DHCP server it leased
the address from.
>3) Just want to know what the DHCP server will do if it
>receives a DHCP renew packet, but the previous IP address
>leased doesn't belong to this server (assume separate IP
>pool). Reject or try to lease another IP address to the client?
#####
Won't happen. As I stated above, the renewal process uses unicast to the
original DHCP server and so the other DHCP servers won't see it. If the
original server goes offline, the lease will expire. Just before the
lease expires the client will start broadcasting DHCP DISCOVER packets
to get a new lease.
>4) What other potential problems when deploying two DHCP relay
>agents on same subnet?
#####
I've set this up a number of times without any problems.
HTH,
Jonathan
>
>Thanks.
>
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