Failure of dhcp server failover

Eugene Grosbein eugen at grosbein.net
Mon May 2 17:43:47 UTC 2016


02.05.2016 2:37, Niall O'Reilly пишет:
> On 1 May 2016, at 19:41, Eugene Grosbein wrote:
>
>> Thank you, this is interesting. But in my case all requests from single AP came with the same gwaddr,
>
>    Ah.  Whenever I have configured Cisco router, I have been able to configure the relay function
>    per-VLAN rather than per port.  If that’s a possibility for you, it may be interesting.  From
>    what you say, router isn’t currently separating the VLANs.

My Cicso router is separating VLANs and relay works per-VLAN. These are just "ip unnumbered" vlans:

interface Loopback2
  description "DHCP default gateway"
  ip address 31.220.160.2 255.255.255.255
  no ip redirects
!
interface Vlan1000
  description "DHCP Guest"
  ip unnumbered Loopback2
  ip helper-address X.X.X.X
  ip helper-address Y.Y.Y.Y
  ip verify unicast source reachable-via rx
!
interface Vlan2000
  description "DHCP Guest"
  ip unnumbered Loopback2
  ip helper-address X.X.X.X
  ip helper-address Y.Y.Y.Y
  ip verify unicast source reachable-via rx
!

The routers also runs DHCP snooping, it sees as DHCP server assigns IP addresses
and installs corresponding /32 route to corresponding network interface and
removes such route later when lease expires. These are standard functions
of Cisco DHCP relaying/snooping.


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