Failover communication
Loren M. Lang
lorenl at north-winds.org
Sun Mar 18 01:44:38 UTC 2012
On 3/14/2012 7:20 AM, Smith Bill wrote:
>
> Hi
>
> Does anyone have any detailed information regarding the communication
> that happens between two dhcp servers configured for failover -- I
> have two servers that don't seem to talk to each other and the tcpdump
> is showing block icmp traffic so I guess I need to know if dhcp
> communicates with its failover partner via icmp.
>
The DHCP Failover protocol uses TCP only. I believe this IETF Internet
Draftdiscusses a proposed version of it, but as it never became an RFC,
it may not be 100% accurate.
http://tools.ietf.org/html/draft-ietf-dhc-failover-12
As for using tcpdump, set a capture filter like "tcp port 9999" and
replace 9999 with the port line you used in the failover peer block from
dhcpd.conf. To analyze the protocol, I recommend using Wireshark. You
can use Wireshark to do the capture directly, or you can tell tcpdump to
save it's capture to a file which Wireshark can open. Use the tcpdump
options "-w dhcp-failover.pcap -s 0" to save it to a file. Wireshark
can decode a decent amount of the protocol and it shouldn't be too hard
to figure out what's wrong. Here's my failover configuration:
failover peer "peer" {
secondary;
address 192.168.1.5;
port 7111;
peer address 192.168.1.7;
peer port 7111;
max-response-delay 60;
max-unacked-updates 10;
mclt 3600;
load balance max seconds 3;
}
> Regards
>
> Bill Smith
>
> Senior Solutions Architect
>
> Architecture & Design H&NS North
>
> Fujitsu Services
>
> Tel: 07867 821165
>
> Email:bill.smith at uk.fujitsu.com
>
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--
Loren M. Lang
lorenl at north-winds.org
http://www.north-winds.org/
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