31 Aug

Reserved VLANs on NX-OS 5.2(1)

Internal VLANs are used for services like MPLS, FCoE, Multicast over GRE, enhancement to SPAN, etc. Some Features have special requirements like which VLAN can be reserved for them. Example of such service are Multicast VLAN which can only start with VLAN id’s that is multiple of 64.

Prior to release 5.2(1) the reserved VLAN range was 3968 to 4048, and 4094, and it was not configurable. After the upgrade user-defined VLANs might fall within the new reserved range which now range from 3968 to 4095 and is configurable. If that occurs, switch fallback to old range but the features that need the additional reserved VLANs won’t work propely. What you have to do is change range of reserved VLANs using command:

switch(config)# system vlan 2000 reserve
This will delete all configs on vlans 2000-2127. Continue anyway? (y/n) [no] y
Note: After switch reload, VLANs 2000-2127 will be reserved for internal use.
      This requires copy running-config to startup-config before
      switch reload. Creating VLANs within this range is not allowed.

Now the disadvantage if this is you have to reboot whole chassis. Simple switchover between supervisors on Nexus 7000 won’t be enough. Also, if you are using vPC if one switch is using new VLAN range and other one is still configured to use old range switches will not forward those VLANs on vPC peer-link. Hence, those VLANs will get suspended on vPC port-channel. But this should not affect any other VLANs in vPC.

14 May

No ISSU on Nexus 7000 with vPC between VDCs on same chassis

If you are using multiple VDCs on your Nexus 7000 switch and you create vPC between two of them you can forget about upgrading NX-OS via ISSU. This scenario is not supported, but there is no information about that in documentation. If you try to perform upgrade you will see following error message:

Notifying services about the switchover.            [#                   ]   0% -- FAIL. Return code 0x401E007B (request was aborted by service).
Please issue "show install all failure-reason" to find the cause of the failure.

Failure recovery action::
"Standby will be rebooted to force netboot and image download".
Install has failed. Return code 0x401E007B (request was aborted by service).

Please identify the cause of the failure, and try 'install all' again.

n7k-switch# show install all failure-reason
Service "vpc" in vdc: 2 returned error: configuration lock can not be acquired for peer switch (x41B7004B)
Service "vpc" in vdc: 3 returned error: configuration lock can not be acquired for peer switch (x41B7004B)

The only way to upgrade is to download new software, replace bootvar and reboot whole chassis.

25 Aug

vPC peer-link on Nexus switches

On Catalyst 6500 platform we had VSS technology that provides redundancy of uplinks with single spanning-tree point. Pair of Nexus switches cannot be one logical devices but with vPC technology those can act as singe spanning-tree point. Idea of redundancy is pretty much similar – downstream switch have two bundled uplinks, one to each uplink switches. If one of links of switches fails traffic is still forwarded using second link. This technology on Nexus switches is called vPC (Virtual PortChannel).
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