DHCP Relay

The statistics show that it received 5 packets in (client), and sent 5 packets out (server). You say you can't see that traffic ? Was that by capturing on the dhcp server, or on the bigip ?

What do you see if you run this on the bigip, whilst making dhcp requests ?

tcpdump -n -i0.0:nnn host 10.2.0.11

There should be some echo requests and replies from the monitor, but also udp traffic heading towards it from the virtual server.

I have captured traffic on two different path locations, shared screen shot is on interface of F5 connected with router (outside network). Which shows traffic is hitting interface (DHCP Discover). While on exit interface I can see normal traffic like ping from F5 to nodes, but no traffic for DHCP (screen shot not shared).

From stats screen (traffic detail) it is showing that packets in are 4 but out are none.

I really stuck on this, want to finish it. It is lab environment.

Best Regards,

Hi i have one important discovery on outside interface, where dhcp clinet exist. Please see attached.

here self ip 172.31.0.145 is doing arp for 172.31.0.151 (dhcp Virtual server IP). But i am not able to see reply back that who owns DHCP VS VIP.

Best Regards,

keep bumping is nice but are you doing anything else?

does it work for http traffic for example?

never build a DHCP virtual server, but i kinda don't expect it on an IP address, are you sure that should work?

Hi, I have build on same lab dns/ftp/ssh/http/https solution. Even i have build DHCP with directly attached client to outside interface. This problem is only occurring if clients are multi hops away from F5. All above stated services are build with success for multi hop away clients. for directly attached client in outside interface vlan i have used 0.0.0.0/0 source and destination 255.255.255.255 and it worked fine.

Best Regards,

Hi F5Drive,

it doesn't make much sense to point the ip helper-address on your switches to a Virtual Server which is configured as DHCP relay. In the best case your setup would confuse your DHCP servers making them unable to identify the remote subnet and to provide a valid IP address from the the right IP scope. And in the worst case it would simply not work and making you angry...

Point the ip-helpers on your switches either directly to each of the individual DHCP servers (you can configure multiple ip-helper on a single VLAN interface) or use a single ip-helper and point them to a Virtual Server that is performing a regular UDP:67 load balancing for your DHCP servers (without SNAT applied). In this case the ip-helper will collect the 255.255.255.255:67 DHCP broadcast and transform it to DHCP unicast (src=IP-Helper:68 and DST=Virtual_Serer:67) so that it can be routed across your network environment and reach your Virtual Servers and finally the load balanced DHCP servers. Also keep in mind, that the clients must be able to directly access the individual DHCP servers for DHCP updates and DHCP Option 81 request, since they would unicast the DHCP server which had assigned their current IP address.

Note: A Virtual Server based DHCP relay configuration should use 255.255.255.255:67 as IP:Port combination. See https://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/ltm-implementations-11-1-0/23.html for further information.

Cheers, Kai

Here's the code we use in 12.1, however i don't believe we changed it from 11.6 to 12.1

ltm virtual dhcp-relay {
    destination 255.255.255.255:bootps
    dhcp-relay
    ip-protocol udp
    mask 255.255.255.255
    pool dhcp-pool
    profiles {
        dhcpv4 { }
    }
    source 0.0.0.0/0
    translate-address enabled
    translate-port disabled
}

HTH

Andrew

Have a try with this config:

ltm virtual dhcp-tcp_vs {
    destination 172.31.0.151:any
    ip-protocol tcp
    mask 255.255.255.255
    pool dhcp-all
    profiles {
        tcp { }
    }
    source 0.0.0.0/0
    source-address-translation {
        type automap
    }
    translate-address enabled
    translate-port disabled
}
ltm virtual dhcp-udp_vs {
    destination 172.31.0.151:any
    ip-protocol udp
    mask 255.255.255.255
    pool dhcp-all
    profiles {
        udp { }
    }
    source 0.0.0.0/0
    source-address-translation {
        type automap
    }
    translate-address enabled
    translate-port disabled
}
ltm virtual dhcp-relay {
    destination 255.255.255.255:bootps
    dhcp-relay
    ip-protocol udp
    mask 255.255.255.255
    pool dhcp-any
    profiles {
        dhcpv4 { }
    }
    source 0.0.0.0/0
    translate-address enabled
    translate-port disabled
}
ltm pool dhcp-any {
    load-balancing-mode least-connections-member
    members {
        DC-11:any {
            address 10.2.0.11
            session monitor-enabled
            state up
        }
        DC-33:any {
            address 10.2.0.33
            session monitor-enabled
            state up
        }
        DC-22:any {
            address 10.2.0.22
            session monitor-enabled
            state up
        }
    }
    monitor gateway_icmp
}

Remember if using tmsh you can use the following command to import the config:

load sys config merge from-terminal

Then just paste the above config in and see how you go.

Cheers,