Chris Adams wrote:

Anybody have any experience with setting up dhcpd in failover mode between two servers? I set this up on a couple of servers, and it seems to be working, but I don't think it is working "right". It appears both servers are replying to all requests (which for renewals works okay because they both give the same address, but new requests get two different responses). I thought that only one server would reply to a particular request.

<snip> In our /etc/dhcp/dhcpd.conf, we have a stanza

failover peer "dhcp" { primary; address <primary IP address; port 519; peer address <failovee peer IP address>; peer port 520; max-response-delay 300; max-unacked-updates 10; mclt 600; split 128; load balance max seconds 3; }

Hope that helps.

mark

In article 20150923194959.GE2874@cmadams.net, Chris Adams linux@cmadams.net wrote:

Anybody have any experience with setting up dhcpd in failover mode between two servers? I set this up on a couple of servers, and it seems to be working, but I don't think it is working "right". It appears both servers are replying to all requests (which for renewals works okay because they both give the same address, but new requests get two different responses). I thought that only one server would reply to a particular request.

Also, every DHCPACK is followed by a message like this in the log:

Sep 23 15:45:50 rad2 dhcpd: bind update on x.x.x.x from mypeer rejected: incoming update is less critical than outgoing update

Any ideas? I subscribed and asked over on the ISC-operated dhcp-users list but haven't had any responses. Google finds others asking about the same log message, and the only responses seem to be "well, if you get it for every update, there's probably some configuration issue" (but nobody ever says what issue might lead to it).

Well it would probably help if you showed us your dhcpd.conf file from each server.

But anyway, if it helps, here is what I have working:

SYSTEM 1 (192.168.100.3) ------------------------

# # DHCP Server Configuration file. # see /usr/share/doc/dhcp*/dhcpd.conf.sample # see 'man 5 dhcpd.conf' #

authoritative; ddns-update-style none;

failover peer "dhcp-failover" { primary; # declare this to be the primary server mclt 1800; # only on primary split 128; # only on primary

#secondary; # declare this to be the secondary server

address 192.168.100.3; # my address port 647; peer address 192.168.100.4; # peer's address peer port 647; max-response-delay 30; max-unacked-updates 10; load balance max seconds 3; }

subnet 192.168.100.0 netmask 255.255.255.0 { option subnet-mask 255.255.255.0; option broadcast-address 192.168.100.255; option routers 192.168.100.1; option domain-name-servers 192.168.100.1; option domain-name "example.co.uk"; pool { failover peer "dhcp-failover"; deny dynamic bootp clients; range 192.168.100.100 192.168.100.149; default-lease-time 86400; max-lease-time 172800; } }

SYSTEM 2 (192.168.100.4) ------------------------

# # DHCP Server Configuration file. # see /usr/share/doc/dhcp*/dhcpd.conf.sample # see 'man 5 dhcpd.conf' #

authoritative; ddns-update-style none;

failover peer "dhcp-failover" { #primary; # declare this to be the primary server #mclt 1800; # only on primary #split 128; # only on primary

secondary; # declare this to be the secondary server

address 192.168.100.4; # my address port 647; peer address 192.168.100.3; # peer's address peer port 647; max-response-delay 30; max-unacked-updates 10; load balance max seconds 3; }

subnet 192.168.100.0 netmask 255.255.255.0 { option subnet-mask 255.255.255.0; option broadcast-address 192.168.100.255; option routers 192.168.100.1; option domain-name-servers 192.168.100.1; option domain-name "example.co.uk"; pool { failover peer "dhcp-failover"; deny dynamic bootp clients; range 192.168.100.100 192.168.100.149; default-lease-time 86400; max-lease-time 172800; } }

Note the differences between the "failover peer" sections. One must say primary, and the other secondary. You must omit mclt and split on the secondary, and must swap the address and peer address over.

Cheers Tony