VSS routing

Shutchis · ‎01-25-2022

Hello, I have a question about the "show platform hardware ip route ipv4" command.

My 2 4507 switches are set up in VSS mode. (VSL link Po1/Po2). Routing protocol is EIGRP. I have 2 circuits from the VSS to a single remote location with 2 core 6509 switches, one circuit on each 6509 (non VSS), inter-connected via port-channel (Po1). The circuits are each assigned a separate SVI, used as the layer 3 interconnect to the remote site.

4507 chassis 1: cct 1 = vlan 200 (local 192.168.54.65, remote 192.168.54.66 on 6509 switch1)

4507 chassis 2: cct 2 = vlan 201 (local 192.168.54.69, remote 192.168.54.70 on 6509 switch 2)

EIGRP says routes to 10.10.10.0/24 are equal cost via either circuit.

The remote 6509s connected via Po1 have HSRP running on the vlan using 10.10.10.0/24. 6509 swicth2 has Active VIP.

My source vlan on 4507 is 10.10.200.0/24, destination subnet at remote site is 10.10.10.0/24.

When I use the cef exact route command on 4507 I can see the exact route bring used to the remote network using circuit 2.

show ip cef exact-route 10.10.200.0 10.10.0.0
10.10.200.0 -> 10.10.0.0 =>IP adj out of Vlan201, addr 192.168.54.70

My question is, how can I tell which route is being used from results below? Which one take precedence?

sho plat hard ip route ipv4 network 10.10.10.0 255.255.255.0

Executing the command on VSS member switch role = VSS Active, id = 2

-----------------------------------------------------------
Block: 0 En: true EntryMap: LSB Width: 80-Bit Type: Dst
-----------------------------------------------------------
000079: v4 10.10.10.0/24 --> vrf: Global Routing Table (1)
adjStats: true fwdSel: 2 Dug: 0 mrpf: 0 (None) fwdIdx: 0 ts: 0
adjIndex: 48118 vlan: 200 port: Po2 (1098)
fwdCtrl: 5 cpucode: 3 sifact4: FwdToCpu sifact6: Fwd load-balances: 2
sa: 00:08:E3:FF:FC:28 da: 00:25:83:24:EC:00

adjIndex: 48119 vlan: 201 port: Te2/3/8 (831)
fwdCtrl: 4 cpucode: 3 sifact4: FwdToCpu sifact6: Fwd load-balances: 1
sa: 00:08:E3:FF:FC:28 da: 00:25:83:24:70:00

Executing the command on VSS member switch role = VSS Standby, id = 1

-----------------------------------------------------------
Block: 0 En: true EntryMap: LSB Width: 80-Bit Type: Dst
-----------------------------------------------------------
000050: v4 10.10.10.0/24 --> vrf: Global Routing Table (1)
adjStats: true fwdSel: 2 Dug: 0 mrpf: 0 (None) fwdIdx: 0 ts: 0
adjIndex: 48012 vlan: 200 port: Te1/3/8 (415)
fwdCtrl: 5 cpucode: 3 sifact4: FwdToCpu sifact6: Fwd load-balances: 2
sa: 00:08:E3:FF:FC:28 da: 00:25:83:24:EC:00

adjIndex: 48013 vlan: 201 port: Po1 (841)
fwdCtrl: 4 cpucode: 3 sifact4: FwdToCpu sifact6: Fwd load-balances: 1
sa: 00:08:E3:FF:FC:28 da: 00:25:83:24:70:00

Thanks for your consideration.

MichaelMcCoy · ‎01-26-2022

Hey please excuse me, I'm a bit of a novice but I read the stress to try to work through troubleshooting to learn. So my advice may be coming from a place of ignorance as even reading your thread you seem to know more than I. With that said could you run a series of commands to include :sh standby" to see which router is active in the HSRP cluster, and then "sh spanning-tree vlan XX" to see which ports are in blocking/forwarding states. I know it's a way to piece it together,a nd maybe you are looking for a single line item, just trying to assist.

Shutchis · ‎01-26-2022

Hi Michael,

6509 switch2 has Active VIP.

S2#sho stand brief
P indicates configured to preempt.
|
Interface Grp Pri P State Active Standby Virtual IP
Vl10 10 110 P Active local 10.10.10.2 10.10.10.1

FH-6509E-S2#sho span vlan 10

VLAN0010
Spanning tree enabled protocol rstp
Root ID Priority 32778
Address 0025.8324.7000
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32778 (priority 32768 sys-id-ext 10)
Address 0025.8324.7000
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 480

Interface Role Sts Cost Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Gi8/10 Desg FWD 20000 128.906 P2p (server)
Po1 Desg FWD 2 128.1665 P2p (to 6509-S1)
Po10 Desg FWD 10000 128.1666 P2p Edge (server)

All ports are forwarding. The show standby results show S2 is the active VIP (S1 is standby) and Spanning-tree looks normal.

The 6509-S2 L3 interconnect to 4507 is SVI 201, addr 192.168.54.70 so the route from the 4507 perspective seems correct. (da: 00:25:83:24:70:00 is 192.168.54.70)

What I don't understand are the results of the "show plat hard ip route ipv4 network 10.10.10.0 255.255.255.0" command and whether it is used to determine the "exact-route".

I have tried searching for documentation on "show platform hardware ip route..." but came up short.

Each chassis in VSS has 2 routes for same destination. (load-balances:2 and load-balances:1).

Does anyone know how to read this?