In the existing environment, they are utilizing Nortel's split multi-link trunking (SMLT) for layer 2 resiliency and aggregation. I have been tasked with setup of the new Nexus switches and configuring a similar topology using Cisco vPC technology for layer 2 resiliency and aggregation.
In this example, we are going to create vPC peer-link and a single LACP port channel to a Nortel 5510 switch.
Let's start with the basic Nexus vPC configuration. I'm not going to spend a lot of time on it as it's been covered by many people.
Nexus-01 feature vpc feature lacp interface mgmt0 ip address 192.168.200.253/24 vpc domain 1 role priority 4096 peer-keepalive destination 192.168.200.253 peer-gateway auto-recovery interface Ethernet1/31 descriptoin vPC Peer Link switchport mode trunk spanning-tree port type network channel-group 1 mode active interface Ethernet1/32 description vPC Peer Link switchport mode trunk spanning-tree port type network channel-group 1 mode active interface port-channel1 switchport mode trunk spanning-tree port type network vpc peer-link interface vlan2 ip address 192.168.10.254/24 standby 2 ip 192.168.10.1 standby 2 priority 110 no shutdown Nexus-02 feature vpc feature lacp interface mgmt0 ip address 192.168.200.254/24 vpc domain 1 role priority 8192 peer-keepalive destination 192.168.200.254 peer-gateway auto-recovery interface Ethernet1/31 descriptoin vPC Peer Link switchport mode trunk spanning-tree port type network channel-group 1 mode active interface Ethernet1/32 description vPC Peer Link switchport mode trunk spanning-tree port type network channel-group 1 mode active interface port-channel1 switchport mode trunk spanning-tree port type network vpc peer-link interface vlan2 ip address 192.168.10.253/24 standby 2 ip 192.168.10.1 no shutdown
And now we confirm that the vPC peer-link is up and working properly.
Nexus-01# sh vpc
Legend:
(*) - local vPC is down, forwarding via vPC peer-link
vPC domain id : 1
Peer status : peer adjacency formed ok
vPC keep-alive status : peer is alive
Configuration consistency status : success
Per-vlan consistency status : success
Type-2 consistency status : success
vPC role : primary
Number of vPCs configured : 1
Peer Gateway : Enabled
Peer gateway excluded VLANs : -
Dual-active excluded VLANs : -
Graceful Consistency Check : Enabled
Auto-recovery status : Enabled (timeout = 240 seconds)
vPC Peer-link status
---------------------------------------------------------------------
id Port Status Active vlans
-- ---- ------ --------------------------------------------------
1 Po1 up 1-2
Nexus-02# sh vpc
Legend:
(*) - local vPC is down, forwarding via vPC peer-link
vPC domain id : 1
Peer status : peer adjacency formed ok
vPC keep-alive status : peer is alive
Configuration consistency status : success
Per-vlan consistency status : success
Type-2 consistency status : success
vPC role : secondary
Number of vPCs configured : 1
Peer Gateway : Enabled
Peer gateway excluded VLANs : -
Dual-active excluded VLANs : -
Graceful Consistency Check : Enabled
Auto-recovery status : Enabled (timeout = 240 seconds)
vPC Peer-link status
---------------------------------------------------------------------
id Port Status Active vlans
-- ---- ------ --------------------------------------------------
1 Po1 up 1-2
And now that the vPC connection is up between the switches, we can configure the port-channel for the Nortel switch.
Nexus-01
interface Ethernet1/1
description Trunk to Nortel Test
switchport trunk allowed vlan 1-2
switchport mode trunk
channel-group 10 mode active
interface port-channel10
description Trunk to Nortel Test
no lacp graceful-convergence
switchport trunk allowed vlan 1-2
switchport mode trunk
vpc 10
Nexus-02
interface Ethernet1/1
description Trunk to Nortel Test
switchport trunk allowed vlan 1-2
switchport mode trunk
channel-group 10 mode active
interface port-channel10
description Trunk to Nortel Test
no lacp graceful-convergence
switchport trunk allowed vlan 1-2
switchport mode trunk
vpc 10
*Update: The configuration "no lacp graceful-convergence" was added to the port channel interfaces. LACP graceful convergence was introduced in version 5.1(3)N1(1) and is on by default. Cisco recommends disabling this feature on port channels connected to non NX-OS devices as it can cause the interfaces to inexplicibly enter a standby state.
And now for the multi-link trunk (MLT) configuration on the Nortel switch.
ip address switch 192.168.10.10 ip address netmask 255.255.255.0 vlan mgmt 2 vlan create 2 type port 1 vlan ports 47-48 tagging unTagPvidOnly vlan members 1 1-48 vlan members 2 47-48 vlan ports 47-48 pvid 1 interface fastEthernet 47-48 lacp key 10 lacp timeout-time short lacp mode active lacp aggregation enable
Note that I left the PVID untagged for the two uplink ports to ensure compatibility with the Nexus switches since Cisco uses the concept of native VLANs on trunk ports. For this example, we are keeping it simple and using VLAN 1 for the native VLAN.
When you configure an LACP key on the Nortel switch, it assigns the unique LACP key to an MLT starting with the highest number MLT (32 in this case) and working backwards. The LACP key is local to the switch or stack and is similar to the channel-group with the Nexus switches. The MLT ID is similar to the port-channel interface on the Nexus switches.
At this point, the port-channel and MLT should be up on all the switches. Let's confirm.
Nexus-01# sh lacp neigh
Flags: S - Device is sending Slow LACPDUs F - Device is sending Fast LACPDUs
A - Device is in Active mode P - Device is in Passive mode
PO10 neighbors
Partner's information
Partner Partner Partner
Port System ID Port Number Age Flags
Eth1/1 32768,0-19-69-a6-4c-0 0x2f 378 SA
LACP Partner Partner Partner
Port Priority Oper Key Port State
32768 0x300a 0x3f
Nexus-02# sh lacp neigh
Flags: S - Device is sending Slow LACPDUs F - Device is sending Fast LACPDUs
A - Device is in Active mode P - Device is in Passive mode
Po10 neighbors
Partner's information
Partner Partner Partner
Port System ID Port Number Age Flags
Eth1/1 32768,0-19-69-a6-4c-0 0x30 692 SA
LACP Partner Partner Partner
Port Priority Oper Key Port State
32768 0x300a 0x3f
Nexus-01# sh vpc
!------Excluded for brevity---------!
vPC status
----------------------------------------------------------------------------
id Port Status Consistency Reason Active vlans
------ ----------- ------ ----------- -------------------------- -----------
10 Po10 up success success 1-2
Nexus-02# sh vpc
!------Excluded for brevity---------!
vPC status
----------------------------------------------------------------------------
id Port Status Consistency Reason Active vlans
------ ----------- ------ ----------- -------------------------- -----------
10 Po10 up success success 1-2
5510-48T-PWR# sh lacp port 47-48
Admin Oper Trunk Partner
Port Priority Lacp A/I Timeout Key Key AggId Id Port Status
---- -------- ------- --- ------- ----- ----- ----- ----- ------- -------
47 32768 Active A Short 10 12298 8224 32 257 Active
48 32768 Active A Short 10 12298 8224 32 16641 Active
As you can see, LACP is up on all switches and vPC 10 is up on both Nexus switches. At this point we can confirm connectivity.
Nexus-01# ping 192.168.10.10 PING 192.168.10.10 (192.168.10.10): 56 data bytes 64 bytes from 192.168.10.10: icmp_seq=0 ttl=63 time=1.697 ms 64 bytes from 192.168.10.10: icmp_seq=1 ttl=63 time=1.305 ms 64 bytes from 192.168.10.10: icmp_seq=2 ttl=63 time=1.287 ms 64 bytes from 192.168.10.10: icmp_seq=3 ttl=63 time=1.329 ms 64 bytes from 192.168.10.10: icmp_seq=4 ttl=63 time=1.393 ms Nexus-02# ping 192.168.10.10 PING 192.168.10.10 (192.168.10.10): 56 data bytes 64 bytes from 192.168.10.10: icmp_seq=0 ttl=62 time=9.314 ms 64 bytes from 192.168.10.10: icmp_seq=1 ttl=62 time=3.379 ms 64 bytes from 192.168.10.10: icmp_seq=2 ttl=62 time=3.349 ms 64 bytes from 192.168.10.10: icmp_seq=3 ttl=62 time=3.354 ms 64 bytes from 192.168.10.10: icmp_seq=4 ttl=62 time=3.352 ms 5510-48T-PWR>ping 192.168.10.1 Host is reachable 5510-48T-PWR>ping 192.168.10.254 Host is reachable 5510-48T-PWR>ping 192.168.10.253 Host is reachable
As we can see, ping works from each of the Nexus switches and from the Nortel switch to each Nexus switch and the shared HSRP IP.
The biggest caveat with this configuration is that you cannot change VLAN assignments on the trunk while LACP is active on the Nortel switch. If you change the allowed VLANs on either side of the trunk, it brings down the LACP neighborship until you disable and re-enable LACP on both uplinks. For this reason, I recommend you set the allowed VLANs on the port-channel on the Nexus switches to prevent the trunk from going down simply by creating a VLAN on the switch.
