{"id":5079,"date":"2015-03-17T14:24:28","date_gmt":"2015-03-17T20:24:28","guid":{"rendered":"http:\/\/gregsowell.com\/?p=5079"},"modified":"2015-03-17T14:24:28","modified_gmt":"2015-03-17T20:24:28","slug":"trunking-to-a-nexus-switch","status":"publish","type":"post","link":"https:\/\/gregsowell.com\/?p=5079","title":{"rendered":"Trunking To A Nexus Switch"},"content":{"rendered":"

\"40<\/a>
40 10Gb ports, of which 16 can run in 1Gb mode. Dual PSU with 5 fans.<\/figcaption><\/figure>
\nI’m using a Nexus 5020, and attempting to trunk a 7606 running service provider code…but for some reason VLANs aren’t passing.<\/p>\n

I issue the following on the 7606:<\/p>\n

7606#show int te1\/1 trunk\r\n\r\nPort                Mode         Encapsulation  Status        Native vlan\r\nTe1\/1               on           802.1q         trunking      1\r\n\r\nPort                Vlans allowed on trunk\r\nTe1\/1               1650-1699\r\n\r\nPort                Vlans allowed and active in management domain\r\nTe1\/1               1650-1653\r\n\r\nPort                Vlans in spanning tree forwarding state and not pruned\r\nTe1\/1               1650-1653<\/code><\/pre>\n
This tells me everything is passing here…what happens when I do the same on the Nexus side:<\/p>\n
Nexus5020# show int e1\/17 trunk\r\n\r\n--------------------------------------------------------------------------------\r\nPort          Native  Status        Port\r\n              Vlan                  Channel\r\n--------------------------------------------------------------------------------\r\nEth1\/17       1       trunking      --\r\n\r\n--------------------------------------------------------------------------------\r\nPort          Vlans Allowed on Trunk\r\n--------------------------------------------------------------------------------\r\nEth1\/17       1,1650-1699\r\n\r\n--------------------------------------------------------------------------------\r\nPort          Vlans Err-disabled on Trunk\r\n--------------------------------------------------------------------------------\r\nEth1\/17       none\r\n\r\n--------------------------------------------------------------------------------\r\nPort          STP Forwarding\r\n--------------------------------------------------------------------------------\r\n\r\n\r\n--------------------------------------------------------------------------------\r\nPort          Vlans in spanning tree forwarding state and not pruned\r\n--------------------------------------------------------------------------------\r\n\r\n--------------------------------------------------------------------------------\r\nPort          Vlans Forwarding on FabricPath\r\n--------------------------------------------------------------------------------\r\nEth1\/17       none<\/code><\/pre>\n
As you can see above, none of the VLANs are “STP Forwarding”…but what could be the problem?<\/p>\n
It turns out that Nexus chassis have a new feature called Bridge Assurance<\/a>.  It is an enhancement that helps protect against unidirectional link failure.  Any port designated as “spanning-tree port type network” has it enabled by default.  It expects that the switch on the other end supports the feature and is sending crafted BPDUs over to you.  If you happen to be trunking to a standard catalyst switch, then it basically blocks all VLANs from passing on the port!  How do we work around it…by disabling it.<\/p>\n
You have to globally disable the feature with:<\/p>\n
no spanning-tree bridge assurance<\/code><\/pre>\n
.
\nMagically, your VLANs will begin passing:<\/p>\n
Nexus5020# show int e1\/17 trunk\r\n\r\n--------------------------------------------------------------------------------\r\nPort          Native  Status        Port\r\n              Vlan                  Channel\r\n--------------------------------------------------------------------------------\r\nEth1\/17       1       trunking      --\r\n\r\n--------------------------------------------------------------------------------\r\nPort          Vlans Allowed on Trunk\r\n--------------------------------------------------------------------------------\r\nEth1\/17       1,1650-1699\r\n\r\n--------------------------------------------------------------------------------\r\nPort          Vlans Err-disabled on Trunk\r\n--------------------------------------------------------------------------------\r\nEth1\/17       none\r\n\r\n--------------------------------------------------------------------------------\r\nPort          STP Forwarding\r\n--------------------------------------------------------------------------------\r\nEth1\/17       1,1650-1653\r\n\r\n--------------------------------------------------------------------------------\r\nPort          Vlans in spanning tree forwarding state and not pruned\r\n--------------------------------------------------------------------------------\r\n\r\n--------------------------------------------------------------------------------\r\nPort          Vlans Forwarding on FabricPath\r\n--------------------------------------------------------------------------------\r\nEth1\/17       none<\/code><\/pre>\n
This seems to be a little documented feature and generally takes a little google-fu to find it.  Good luck and happy switching my friends.<\/p>\n","protected":false},"excerpt":{"rendered":"
I’m using a Nexus 5020, and attempting to trunk a 7606 running service provider code…but for some reason VLANs aren’t passing. I issue the\u2026<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[16,20,8],"tags":[],"class_list":["post-5079","post","type-post","status-publish","format-standard","hentry","category-cisco","category-hardware","category-networking"],"_links":{"self":[{"href":"https:\/\/gregsowell.com\/index.php?rest_route=\/wp\/v2\/posts\/5079","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/gregsowell.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/gregsowell.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/gregsowell.com\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/gregsowell.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=5079"}],"version-history":[{"count":1,"href":"https:\/\/gregsowell.com\/index.php?rest_route=\/wp\/v2\/posts\/5079\/revisions"}],"predecessor-version":[{"id":5082,"href":"https:\/\/gregsowell.com\/index.php?rest_route=\/wp\/v2\/posts\/5079\/revisions\/5082"}],"wp:attachment":[{"href":"https:\/\/gregsowell.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=5079"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/gregsowell.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=5079"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/gregsowell.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=5079"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}