I have a router that I have added ip helper addresses to for dhcp use. It is up and working but I ran into a snag in the process that I have yet to figure out. Originally I had planned on adding the helper addresses to the existing 172.16.21.1/24 range (gig 0/1.2) & segmenting the dhcp scope to retain some static IPs that were still in the range. For a reason I have yet to identify with the helper addresses applied to gig 0/1.2 the router would not pass dhcp requests upstream through the tunnel. I then added the range 172.16.27.1/24 (gig 0/1.4) to the router, added permits to the PIX as needed & configured IP helper addresses pointing to our dhcp servers & it worked.
The tunnel terminates into a cisco PIX firewall.
Any ideas as to why dhcp requests would not be passed on gig 0/1.2?
The config below is from the live running config, it doesn't show it now, but I did have the helper addresses on gig 0/1.2 prior to creation of gig 0/1.4.
Are there any common causes that would prevent ip helper addresses from working?
ip subnet-zero
!
ip cef
!
crypto keyring AAAA vrf dn
local-address GigabitEthernet0/0
pre-shared-key address XXXXXXXXXX key XXXXXXXXX
pre-shared-key hostname XXXXXXXXXXX key XXXXXXXXXX
!
crypto isakmp policy 5
encr 3des
hash md5
authentication pre-share
crypto isakmp profile AAAA
vrf dn
keyring AAAA
self-identity address
match identity host XXXXXXXX dn
match identity address 204.61.1.36 255.255.255.255 dn
!
!
crypto ipsec transform-set AAAA esp-3des esp-md5-hmac
!
crypto map AAAA-map 10 ipsec-isakmp
set peer 204.61.1.36
set transform-set AAAA
set isakmp-profile AAAA
match address 120
!
interface Tunnel0
ip address 10.13.2.1 255.255.0.0
no ip redirects
ip nhrp map 10.13.0.1 164.58.245.58
ip nhrp map multicast 164.58.245.58
ip nhrp network-id 507813
ip nhrp holdtime 300
ip nhrp nhs 10.13.0.1
no ip route-cache cef
no ip split-horizon eigrp 13
tunnel source GigabitEthernet0/0
tunnel mode gre multipoint
tunnel key XXXXXXXXXX
tunnel vrf dn
!
interface Loopback0
ip address 10.14.2.1 255.255.255.255
h323-gateway voip bind srcaddr 10.14.2.1
!
interface GigabitEthernet0/0
ip vrf forwarding dn
ip address NNN.NNN.NNN.NNN 255.255.255.252
no ip redirects
ip virtual-reassembly
duplex auto
speed auto
no mop enabled
crypto map AAAA-map
!
interface GigabitEthernet0/1
description Internal LAN
no ip address
no ip redirects
duplex auto
speed auto
no mop enabled
!
interface GigabitEthernet0/1.2
description Data Network
encapsulation dot1Q 2
ip vrf forwarding dn
ip address 172.16.21.1 255.255.255.0
no snmp trap link-status
!
interface GigabitEthernet0/1.3
description IP Phones
encapsulation dot1Q 3
ip address 10.80.2.1 255.255.255.0
no snmp trap link-status
!
interface GigabitEthernet0/1.4
description Data Network for DHCP
encapsulation dot1Q 27
ip vrf forwarding dn
ip address 172.16.27.1 255.255.255.0
ip helper-address 10.100.0.10
ip helper-address 10.100.0.11
ip helper-address 10.100.0.12
no snmp trap link-status
!
router eigrp 13
network 10.13.0.0 0.0.255.255
network 10.14.2.1 0.0.0.0
network 10.80.2.0 0.0.0.255
no auto-summary
neighbor 10.13.0.1 Tunnel0
!
ip classless
ip route vrf dn 0.0.0.0 0.0.0.0 NNN.NNN.NNN.NNN
!
ip nat inside source list 2 interface GigabitEthernet0/0 vrf dn overload
!
access-list 120 permit ip 172.16.21.0 0.0.0.255 any
access-list 120 permit ip 172.16.27.0 0.0.0.255 any
