Nortel 5530 DHCP Relay

[david_vega]

Need expertise on a problem I am facing with Nortel 5530. Vlan are configured and 5530 is trunking to Cisco 6509 Core. Can ping across client on both switches with static addresses. When I plug a host into Nortel 5530 access ports, client does not get IP address from DHCP server. Want the Nortel to function as L2 switch only to pass information to Cisco Core, but isn't working if I don't create SVI corresponding to L2 vlan and set dhcp-relay fwd-path. SVI on Cisco 6509 has helper address, but clients not receiving address unless SVI are created on Nortel 5530 with dhcp fwd relay command. Is there something blocking Discover messages on Nortel 5530? Please advice.

[Michael McNamara]

Hi David and welcome to the forums!

If every thing is configured properly on the 802.1q trunk port between the two switches then there is nothing additional required beyond a DHCP relay agent (helper address) on the C6509 to get the DHCP discover (broadcasts) to be forwarded by the C6509.

Any chance you could post some portions of the configuration here?

What VLAN ID are you using as the access VLAN on the 5530 edge switch ports?

Is that the same VLAN ID as is configured on the C6509?

Do you have the link between the two switches configured as a trunk (802.1q)? (Cisco = Trunk, Nortel = TagAll)

I'm assuming that if you connect a PC to a switch port on the C6509 that's in the same VLAN it gets a DHCP address (as it should)? This proves out the C6509 configuration and the DHCP server configuration.

Cheers!

[david_vega]

First, I would like to appologize for emailing you directly. New to blogs... Didn't know how to use it. I forced myself to learn. LOL. Thanks for the link. Here is the config.

NORTEL 5530

interface vlan 910
ip address 172.18.91.1 255.255.255.0
ip default-gateway 172.18.91.254
exit

vlan mgmt 910

vlan create 1000 name natv type port
vlan create 110 name 110 type port
vlan create 210 name 210 type port
vlan create 310 name 310 type port
vlan create 410 name 410 type port
vlan create 510 name 510 type port
vlan create 2 name guest type port

spanning-tree mode rstp


vlan ports 1/12-26,2/47-48 tagging enable
vlan ports 1/12-26,2/47-48 tagging tagall

vlan ports 1/11 pvid 910 name mgmt-port
vlan ports 1/12 pvid 1000 name monitor-port
vlan ports 1/25 pvid 1000 name trunk-port13
vlan ports 1/26 pvid 1000 name trunk-port14
vlan ports 2/47 pvid 1000 name trunk-port15
vlan ports 2/48 pvid 1000 name trunk-port16
vlan ports 2/43 pvid 2 name guest-port1
vlan ports 2/44 pvid 2 name guest-port2
vlan ports 2/45 pvid 2 name guest-port3
vlan ports 2/46 pvid 2 name guest-port4
vlan ports 2/1 pvid 110 name u1-port1
vlan ports 2/2 pvid 210 name u2-port1
vlan ports 1/1-10,2/3-42 pvid 310

vlan members add 2 1/12-26,2/43-48
vlan members add 110 1/12-26,2/1,2/47-48
vlan members add 210 1/12-26,2/2,2/47-48
vlan members add 310 1/1-10,1/12-26,2/3-42,2/47-48
vlan members add 910 1/11-26,2/47-48
vlan members add 1000 1/12-26,2/47-48

_________________________________________

CISCO 6509E

interface ten3/1
switchport
switchport tru en do
switchport mod tru
switchport no
switchport tru nat vlan 1000
switchport trunk allowed vlan 1,2,5,1000,110,210,310,410,510,910
no shutdown

vlan 110,210,310,910,1000

interface vlan 110
ip address 172.18.11.254 255.255.255.0
ip helper-address 172.16.16.100

interface vlan 210
ip address 172.18.21.254 255.255.255.0
ip helper-address 172.16.16.100

interface vlan 310
ip address 172.18.31.254 255.255.255.0
ip helper-address 172.16.16.100

interface vlan 910
ip address 172.18.91.254 255.255.255.0
ip helper-address 172.16.16.100

[Michael McNamara]

What ports are you connecting between the C6509 and the ERS5530?

What port are you using to connect your client device on the ERS 5530?

Cheers!

[david_vega]

Clients connecting to 2/1(vlan 110),2/2(vlan210),2/10(vlan310) on Nortel 5510-48 that is stacked with 5530. have also tried changing vlan members & pvid on 5530 and connecting hosts to assigned ports. No ip received via dhcp. Not sure what step I am missing on 5530 configuration.

CISCO Core Trunking from Ten3/1 to 1/26 on Nortel 5530

fyi, validated dhcp scope are configured correctly on MS DHCP server. Cisco 3560 connecting to Cisco 6509E via EIGRP is able to relay DHCP Messages and clients are receive ip address.

[Michael McNamara]

It looks like everything is in place.

When you say it works with a 3560E, are you running that 3560E as a Layer 2 switch or as a Layer 3 switch? I ask because you reference EIGRP which makes me believe you have a DHCP relay agent (helper address) on the 3560E itself.

If you have an idle Ethernet switchport on your C6509 why not just make it a member of VLAN 110 (switchport mode access vlan 110) and then plugin your test PC and make sure that it get's a DHCP response.

Short of that your going to have to-do some extensive troubleshooting. If you have access to the DHCP server perhaps you can check the logs (or better yet turn up the debug log level) so you can see if the DHCP request is even making it to the DHCP server. You'll probably need to setup a SPAN (port mirror) on the C6509 to see if the DHCP broadcast packet is making it to the C6509.

Sorry I can offer more help. I have an ERS 5520 (Layer 2) trunked to a Cisco Nexus 7010 and it works fine.

Good Luck!

[david_vega]

Found the underlying issue... I had locked down the Cisco 6509E Core which included the command "no service dhcp". reenabled the service and the relay worked from Nortel Switches... Sorry for the trouble, but I hope this will help another person who is facing this problem. LOL. All engineers make mistakes...

[Michael McNamara]

Thanks for posting the follow-up.

Cheers!