DHCP Relay

[InfrArch]

Helo,
How can I configure DHCP Relay agent on Cisco 2500 router fastethernet interface. I tryed to set ip helper-address x.x.x.x , where x.x.x.x is an IP of my dhcp in other subnet. But it does not work.

Victor K
psas@canada.com
MCSE+I;MCSA;MCSE(w2k);CNE(5.1);MCNE(6);CIWSP;CIWSA.

 

[gaveeve]

If the ip helper-address is configured correctly then #show ip interface (your ethernet interface), will show
"Helper addresses are xxxx.xxxx.xxxx.xxxx". I would check that and if that is configured correctly move on to looking at how your DHCP is set up.

 

[InfrArch]

Thanks, gaveeve

Router config is OK. DHCP - is a MS W2k DHCP that works fine. But unfortunately ip helper-address does not work.
any other ideas?

Victor K
psas@canada.com
MCSE+I;MCSA;MCSE(w2k);CNE(5.1);MCNE(6);CIWSP;CIWSA.

 

[byteya]

Is there a scope set up for the network that you are giving ip addresses to? The DHCP server gets the information from the router of the client's network information. If you don't have a defined scope for that network, it won't give an addresses out.
*J*

 

[svermill]

Are you forwarding to the subnet or the actual server? If broadcast you may need to add:

'ip directed-broadcast'

on both interfaces (the one forwarding the request and the one receiving it).

 

[InfrArch]

Ofcourse there is a scopes for all the subnets. There is NO problems with DHCP configuration.
Svermill: in ip helper-address i'm forwarding directly to the DHCP server's IP address that locates in other subnet. I can ping this address without any problem, so connectivity is not an issue. ip directed-broadcast - on the interface show me , that I must enter some access lists parameters. I'm not familiar with it . can i simply set up to forward ALL broadcasts to the DHCP server. May be it will help.
keeg: couldn't you please write a step by step guide, because I never even tryed to configure Catalyst Switches.

To All: thanks guys! hmm.. definitely , it is necessary to obtain CCNA/CCDA and then CCDP/CCNP certifications.
Victor K
psas@canada.com
MCSE+I;MCSA;MCSE(w2k);CNE(5.1);MCNE(6);CIWSP;CIWSA.

 

[jmrobins]

I am having similar trouble on a Catalyst 2948g - we are terminating several VLANs from remote bootp devices (Nortel 1-Meg Modem DBIC's). We have a handful of ones that will not boot because our bootp server never receives a request from the DBIC... We have taken the catalyst out and proven that the requests are arriving, just not being forwarded. Below is our configuration...sorry it is so long... Any help would be GREATLY appreciated!

We are currently working with fa46 - the two interfaces giving us problems are fa46.21 and fa46.22. The rest seem to work...however it seems fairly eratic. Our BOOTP server (10.10.0.3) is connected via bvi1.

Thanks!

Justin Robinson


VTelGateway#write t
Building configuration...

Current configuration:
!
version 12.0
no service pad
service timestamps debug uptime
service timestamps log datetime
service password-encryption
!
hostname VTelGateway
!
enable secret 5 XXXXXXXXXXXXXXXXXxx
!
username XXXXXX password 7 XXXXXXXXXXXXXXXXXXx
username XXXXX password 7 XXXXXXXXXXXXXXXXx
sdm size ipx-bvi-network 32
sdm size ip-adjacency 2048
sdm size ipx-node 2048
sdm size ip-prefix 8192
sdm size ipx-network 6144
sdm size ip-mcast 3072
sdm size udp-flooding 256
sdm size l2-switching 1024
no sdm autolearn
ip subnet-zero
ip name-server 10.10.0.3
ip name-server 216.66.108.26
bridge irb
!
!
!
interface FastEthernet1
no ip address
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet2
no ip address
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet3
no ip address
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet4
no ip address
no ip directed-broadcast
no bridge-group 1
!
interface FastEthernet5
no ip address
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet6
no ip address
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet7
no ip address
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet8
no ip address
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet9
no ip address
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet10
no ip address
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet11
no ip address
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet12
no ip address
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet13
no ip address
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet14
no ip address
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet15
no ip address
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet16
no ip address
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet17
no ip address
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet18
no ip address
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet19
no ip address
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet20
no ip address
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet21
no ip address
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet22
no ip address
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet23
no ip address
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet24
no ip address
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet25
no ip address
no ip directed-broadcast
shutdown
!
interface FastEthernet26
no ip address
no ip directed-broadcast
shutdown
!
interface FastEthernet27
no ip address
no ip directed-broadcast
shutdown
!
interface FastEthernet28
no ip address
no ip directed-broadcast
shutdown
!
interface FastEthernet29
no ip address
no ip directed-broadcast
shutdown
!
interface FastEthernet30
no ip address
no ip directed-broadcast
shutdown
!
interface FastEthernet31
no ip address
no ip directed-broadcast
shutdown
!
interface FastEthernet32
no ip address
no ip directed-broadcast
shutdown
!
interface FastEthernet33
no ip address
no ip directed-broadcast
shutdown
!
interface FastEthernet34
no ip address
no ip directed-broadcast
shutdown
!
interface FastEthernet35
no ip address
no ip directed-broadcast
shutdown
!
interface FastEthernet36
no ip address
no ip directed-broadcast
shutdown
!
interface FastEthernet37
no ip address
no ip directed-broadcast
shutdown
!
interface FastEthernet38
no ip address
no ip directed-broadcast
shutdown
!
interface FastEthernet39
no ip address
no ip directed-broadcast
shutdown
!
interface FastEthernet40
no ip address
no ip directed-broadcast
shutdown
!
interface FastEthernet41
no ip address
no ip directed-broadcast
shutdown
!
interface FastEthernet42
no ip address
no ip directed-broadcast
shutdown
!
interface FastEthernet43
no ip address
no ip redirects
no ip directed-broadcast
!
interface FastEthernet43.1
encapsulation dot1Q 1099
no ip redirects
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet43.3
encapsulation dot1Q 1139
no ip redirects
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet43.4
encapsulation dot1Q 1119
no ip redirects
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet44
no ip address
no ip redirects
no ip directed-broadcast
!
interface FastEthernet44.1
encapsulation dot1Q 1199
no ip redirects
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet44.2
encapsulation dot1Q 1149
no ip redirects
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet44.3
encapsulation dot1Q 1189
no ip redirects
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet44.4
encapsulation dot1Q 1169
no ip redirects
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet44.5
encapsulation dot1Q 1129
no ip redirects
no ip directed-broadcast
bridge-group 1
!
interface FastEthernet45
no ip address
no ip redirects
no ip directed-broadcast
!
interface FastEthernet45.1
encapsulation dot1Q 1071
no ip redirects
no ip directed-broadcast
bridge-group 4
!
interface FastEthernet45.2
encapsulation dot1Q 1072
no ip redirects
no ip directed-broadcast
bridge-group 4
!
interface FastEthernet45.3
encapsulation dot1Q 1073
no ip redirects
no ip directed-broadcast
bridge-group 4
!
interface FastEthernet45.4
encapsulation dot1Q 1074
no ip redirects
no ip directed-broadcast
bridge-group 4
!
interface FastEthernet45.5
encapsulation dot1Q 1075
no ip redirects
no ip directed-broadcast
bridge-group 4
!
interface FastEthernet45.6
encapsulation dot1Q 1076
no ip redirects
no ip directed-broadcast
bridge-group 4
!
interface FastEthernet45.7
encapsulation dot1Q 1077
no ip redirects
no ip directed-broadcast
bridge-group 4
!
interface FastEthernet45.8
encapsulation dot1Q 1078
no ip redirects
no ip directed-broadcast
bridge-group 4
!
interface FastEthernet45.9
encapsulation dot1Q 1079
no ip redirects
no ip directed-broadcast
bridge-group 4
!
interface FastEthernet45.10
encapsulation dot1Q 1080
no ip redirects
no ip directed-broadcast
bridge-group 4
!
interface FastEthernet45.11
encapsulation dot1Q 1081
no ip redirects
no ip directed-broadcast
bridge-group 4
!
interface FastEthernet45.12
encapsulation dot1Q 1082
no ip redirects
no ip directed-broadcast
bridge-group 4
!
interface FastEthernet45.13
encapsulation dot1Q 1101
no ip redirects
no ip directed-broadcast
bridge-group 4
!
interface FastEthernet45.14
encapsulation dot1Q 1102
no ip redirects
no ip directed-broadcast
bridge-group 4
!
interface FastEthernet45.15
encapsulation dot1Q 1103
no ip redirects
no ip directed-broadcast
bridge-group 4
!
interface FastEthernet45.16
encapsulation dot1Q 1104
no ip redirects
no ip directed-broadcast
bridge-group 4
!
interface FastEthernet45.17
encapsulation dot1Q 1105
no ip redirects
no ip directed-broadcast
bridge-group 4
!
interface FastEthernet45.18
encapsulation dot1Q 1106
no ip redirects
no ip directed-broadcast
bridge-group 4
!
interface FastEthernet45.19
encapsulation dot1Q 1107
no ip redirects
no ip directed-broadcast
bridge-group 4
!
interface FastEthernet45.20
encapsulation dot1Q 1131
no ip redirects
no ip directed-broadcast
bridge-group 4
!
interface FastEthernet45.21
encapsulation dot1Q 1132
no ip redirects
no ip directed-broadcast
bridge-group 4
!
interface FastEthernet45.22
encapsulation dot1Q 1141
no ip redirects
no ip directed-broadcast
bridge-group 4
!
interface FastEthernet45.23
encapsulation dot1Q 1142
no ip redirects
no ip directed-broadcast
no cdp enable
bridge-group 4
!
interface FastEthernet46
no ip address
no ip redirects
no ip directed-broadcast
!
interface FastEthernet46.1
description Sunnrise DBIC 00-0-18 00-0-19
encapsulation dot1Q 1121
no ip redirects
no ip directed-broadcast
bridge-group 3
!
interface FastEthernet46.2
description Sherburne DBIC 01-1-18 01-1-19
encapsulation dot1Q 1151
ip address 172.19.6.1 255.255.255.252
ip helper-address 10.10.0.3
no ip redirects
no ip directed-broadcast
!
interface FastEthernet46.3
description Sherburne DBIC 01-1-16 01-1-17
encapsulation dot1Q 1152
ip address 172.19.7.1 255.255.255.252
ip helper-address 10.10.0.3
no ip redirects
no ip directed-broadcast
!
interface FastEthernet46.6
description Sherburne DBIC 01-1-10 01-1-11
encapsulation dot1Q 1155
ip address 172.19.10.1 255.255.255.252
ip helper-address 10.10.0.3
no ip redirects
no ip directed-broadcast
!
interface FastEthernet46.7
encapsulation dot1Q 1171
no ip redirects
no ip directed-broadcast
bridge-group 3
!
interface FastEthernet46.8
encapsulation dot1Q 1172
no ip redirects
no ip directed-broadcast
bridge-group 3
!
interface FastEthernet46.9
encapsulation dot1Q 1173
no ip redirects
no ip directed-broadcast
bridge-group 3
!
interface FastEthernet46.10
encapsulation dot1Q 1174
no ip redirects
no ip directed-broadcast
bridge-group 3
!
interface FastEthernet46.11
encapsulation dot1Q 1175
no ip redirects
no ip directed-broadcast
bridge-group 3
!
interface FastEthernet46.12
no ip redirects
no ip directed-broadcast
!
interface FastEthernet46.13
encapsulation dot1Q 1177
no ip redirects
no ip directed-broadcast
bridge-group 3
!
interface FastEthernet46.14
encapsulation dot1Q 1178
no ip redirects
no ip directed-broadcast
bridge-group 3
!
interface FastEthernet46.15
encapsulation dot1Q 1179
no ip redirects
no ip directed-broadcast
bridge-group 3
!
interface FastEthernet46.16
encapsulation dot1Q 1180
no ip redirects
no ip directed-broadcast
bridge-group 3
!
interface FastEthernet46.17
description Mount Holly DBIC 00-0-18 00-0-19
encapsulation dot1Q 1191
ip address 172.19.1.1 255.255.255.252
ip helper-address 10.10.0.3
no ip redirects
no ip directed-broadcast
!
interface FastEthernet46.18
description Mount Holly DBIC 00-0-16 00-0-17
encapsulation dot1Q 1192
ip address 172.19.2.1 255.255.255.252
ip helper-address 10.10.0.3
no ip redirects
no ip directed-broadcast
!
interface FastEthernet46.19
description Mount Holly DBIC 00-0-14 00-0-15
encapsulation dot1Q 1193
ip address 172.19.3.1 255.255.255.252
ip helper-address 10.10.0.3
no ip redirects
no ip directed-broadcast
!
interface FastEthernet46.20
description Sunnrise DBIC 00-0-16 00-0-17
encapsulation dot1Q 1122
no ip redirects
no ip directed-broadcast
bridge-group 3
!
interface FastEthernet46.21
description Sherburne DBIC 01-1-12 01-1-13
encapsulation dot1Q 1153
ip address 172.19.8.1 255.255.255.252
ip helper-address 10.10.0.3
no ip redirects
no ip directed-broadcast
!
interface FastEthernet46.22
description Sherburne DBIC 01-1-14 01-1-15
encapsulation dot1Q 1154
ip address 172.19.9.1 255.255.255.252
ip helper-address 10.10.0.3
no ip redirects
no ip directed-broadcast
!
interface FastEthernet47
no ip address
no ip redirects
no ip directed-broadcast
!
interface FastEthernet47.1
encapsulation dot1Q 1038
no ip redirects
no ip directed-broadcast
bridge-group 2
!
interface FastEthernet47.2
encapsulation dot1Q 1039
no ip redirects
no ip directed-broadcast
bridge-group 2
!
interface FastEthernet47.3
encapsulation dot1Q 1040
no ip redirects
no ip directed-broadcast
bridge-group 2
!
interface FastEthernet47.4
encapsulation dot1Q 1041
no ip redirects
no ip directed-broadcast
bridge-group 2
!
interface FastEthernet47.5
encapsulation dot1Q 1042
no ip redirects
no ip directed-broadcast
bridge-group 2
!
interface FastEthernet47.6
encapsulation dot1Q 1043
no ip redirects
no ip directed-broadcast
bridge-group 2
!
interface FastEthernet47.7
encapsulation dot1Q 1044
no ip redirects
no ip directed-broadcast
bridge-group 2
!
interface FastEthernet47.8
encapsulation dot1Q 1045
no ip redirects
no ip directed-broadcast
bridge-group 2
!
interface FastEthernet48
no ip address
no ip redirects
no ip directed-broadcast
no cdp enable
!
interface FastEthernet48.1
encapsulation dot1Q 1011
no ip redirects
no ip directed-broadcast
bridge-group 6
!
interface FastEthernet48.2
encapsulation dot1Q 1012
no ip redirects
no ip directed-broadcast
bridge-group 6
!
interface FastEthernet48.3
encapsulation dot1Q 1013
no ip redirects
no ip directed-broadcast
bridge-group 6
!
interface FastEthernet48.4
encapsulation dot1Q 1014
no ip redirects
no ip directed-broadcast
bridge-group 6
!
interface FastEthernet48.5
encapsulation dot1Q 1015
no ip redirects
no ip directed-broadcast
bridge-group 6
!
interface FastEthernet48.6
encapsulation dot1Q 1016
no ip redirects
no ip directed-broadcast
bridge-group 6
!
interface FastEthernet48.7
encapsulation dot1Q 1017
no ip redirects
no ip directed-broadcast
bridge-group 6
!
interface FastEthernet48.8
encapsulation dot1Q 1018
no ip redirects
no ip directed-broadcast
bridge-group 6
!
interface FastEthernet48.9
encapsulation dot1Q 1019
no ip redirects
no ip directed-broadcast
no cdp enable
bridge-group 6
!
interface FastEthernet48.10
encapsulation dot1Q 1020
no ip redirects
no ip directed-broadcast
bridge-group 6
!
interface FastEthernet48.11
encapsulation dot1Q 1021
no ip redirects
no ip directed-broadcast
bridge-group 6
!
interface FastEthernet48.12
encapsulation dot1Q 1022
no ip redirects
no ip directed-broadcast
bridge-group 6
!
interface FastEthernet48.13
encapsulation dot1Q 1023
no ip redirects
no ip directed-broadcast
bridge-group 6
!
interface FastEthernet48.14
encapsulation dot1Q 1024
no ip redirects
no ip directed-broadcast
bridge-group 6
!
interface FastEthernet48.15
encapsulation dot1Q 1025
no ip redirects
no ip directed-broadcast
no cdp enable
bridge-group 6
!
interface FastEthernet48.16
encapsulation dot1Q 1026
no ip redirects
no ip directed-broadcast
bridge-group 6
!
interface FastEthernet48.17
encapsulation dot1Q 1027
no ip redirects
no ip directed-broadcast
bridge-group 6
!
interface FastEthernet48.18
encapsulation dot1Q 1028
no ip redirects
no ip directed-broadcast
bridge-group 6
!
interface FastEthernet48.19
encapsulation dot1Q 1029
no ip redirects
no ip directed-broadcast
bridge-group 6
!
interface FastEthernet48.20
encapsulation dot1Q 1030
no ip redirects
no ip directed-broadcast
bridge-group 6
!
interface FastEthernet48.21
encapsulation dot1Q 1031
no ip redirects
no ip directed-broadcast
bridge-group 6
!
interface FastEthernet48.22
encapsulation dot1Q 1032
no ip redirects
no ip directed-broadcast
bridge-group 6
!
interface FastEthernet48.23
encapsulation dot1Q 1033
no ip redirects
no ip directed-broadcast
bridge-group 6
!
interface FastEthernet48.24
encapsulation dot1Q 1034
no ip redirects
no ip directed-broadcast
bridge-group 6
!
interface FastEthernet48.25
encapsulation dot1Q 1035
no ip redirects
no ip directed-broadcast
bridge-group 6
!
interface FastEthernet48.26
encapsulation dot1Q 1036
no ip redirects
no ip directed-broadcast
bridge-group 6
!
interface FastEthernet48.27
encapsulation dot1Q 1037
no ip redirects
no ip directed-broadcast
bridge-group 6
!
interface GigabitEthernet49
no ip address
no ip directed-broadcast
no ip route-cache cef
shutdown
!
interface GigabitEthernet50
no ip address
no ip directed-broadcast
shutdown
!
interface BVI1
ip address 10.10.0.4 255.255.255.0
no ip directed-broadcast
no ip route-cache cef
!
interface BVI2
ip address 172.18.4.33 255.255.255.224
ip helper-address 10.10.0.3
no ip directed-broadcast
no ip route-cache cef
!
interface BVI3
ip address 172.18.17.33 255.255.255.224
ip helper-address 10.10.0.3
no ip directed-broadcast
no ip route-cache cef
!
interface BVI4
ip address 172.18.33.33 255.255.255.224 secondary
ip address 172.18.18.33 255.255.255.224 secondary
ip address 172.18.177.33 255.255.255.224
ip helper-address 10.10.0.3
no ip directed-broadcast
no ip route-cache cef
!
interface BVI6
ip address 172.18.1.33 255.255.255.224
ip helper-address 10.10.0.3
no ip directed-broadcast
no ip route-cache cef
!
ip classless
ip route 0.0.0.0 0.0.0.0 10.10.0.1
!
bridge 1 protocol ieee
bridge 1 route ip
bridge 2 protocol ieee
bridge 2 route ip
bridge 3 protocol ieee
bridge 3 route ip
bridge 4 protocol ieee
bridge 4 route ip
bridge 6 protocol ieee
bridge 6 route ip
!
line con 0
transport input none
line aux 0
line vty 0 4
password 7 0014440E05483C5652
login local
!
end

VTelGateway#

 

[svermill]

jmrobins,

Highjacking of threads is a no-no. Things get too confused. Please start your own.

VictorKozlov,

You can forward broadcasts other than bootp. I don't have a config handy and I'm on my way to a job site. Search on

http://www.cisco.com

for "directed-broadcast 2500." But it won't help. All you need for DHCP to work is forwarding of UDP ports 67 & 68, which are by default enabled when you turn on helper address. The portfast suggestion is a good one. If that is your problem, you should be able to go to a command prompt a few minutes after the machine has booted and issue 'ip config /renew' and you should get a lease (after a few minutes, spanning tree has taken the port out of blocking). If that doesn't work, portfast probably isn't your problem (although it still should be enabled no matter what on ports that connect to PCs). It may be time to get familiar with ethereal (

http://www.ethereal.com).

This will help you figure out where things are breaking.