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New Member

Nexus 5596/2248 pair with 4900M pair

Wanted to get some oversight in on a design I am working on.

I have a pair of 5596's and a pair of 2248 FEX's dual homed to them. I am using 5.1.3 so can also use Host vPC on the dual homed 2248s. VPC VLAN's are on the VPC peer link @ 20Gbps. The 5596 pair has the L3 card installed and does InterVLAN routing for the VPC VLANs.  I created a 2nd 20Gbps trunk for a single NON VPC VLAN that we use as a "routing VLAN" to form adjacencies. This is VLAN 511 and it only exists on this trunk between the two.

At another site I have a pair of 4900m's. I have direct fiber to the site with the 5596's. I want to connect them at Layer 2 and use the VLAN 511 SVI on the 5596's and 4900m's for routing. I know the "rule" is L3 PTP links for this, but using my non VPC VLAN trunk on the 5596's gets around the problem that causes the  "L3 only" recommendation.

Example:

5k1:

int po10

switch mode trunk

switch trunk allowed vlan 511

int e1/10

desc to 4k1

switch mode trunk

channel-gr 10

int e1/11

desc to 4k1

switch mode trunk

channel-gr 10

int po11

switch mode trunk

switch trunk allowed vlan 511

int e1/12

desc to 5k2

switch mode trunk

channel-gr 11

int e1/13

desc to 5k2

switch mode trunk

channel-gr 11

5k2:

int po10

switch mode trunk

switch trunk allowed vlan 511

int e1/10

desc to 4k2

switch mode trunk

channel-gr 10

int e1/11

desc to 4k2

switch mode trunk

channel-gr 10

int po11

switch mode trunk

switch trunk allowed vlan 511

int e1/12

desc to 5k1

switch mode trunk

channel-gr 11

int e1/13

desc to 5k1

switch mode trunk

channel-gr 11

4k1:

int po10

switch mode trunk

switch trunk allowed vlan 511

int te1/1

desc to 5k1

switch mode trunk

channel-gr 10

int te1/2

desc to 5k1

switch mode trunk

channel-gr 10

4k2:

4k1:

int po10

switch mode trunk

switch trunk allowed vlan 511

int te1/1

desc to 5k2

switch mode trunk

channel-gr 10

int te1/2

desc to 5k2

switch mode trunk

channel-gr 10

It seems this would establish all the adjacencies. All switches would peer with all switches using EIGRP.

It also should not bother the VPC VLAN's since this VLAN is not present on the peer link nor any member ports.

Beyond the 4900m's I have many other direct connect fiber sites with 3750's. Each 3750 will have 1 link to each 4900 for redundancy, as well as the special routing VLAN 511. This makes 4900 act as a collapsed core. All sites ONLY trunk 511 to the 4900s. The 4900 performs some local L3 functionality but L2 switches between all the sites. The 4900m is the RSTP root for all VLANs that is has. VLAN 511 only exists on the 4900s and the 5596's. It is blocked everywhere else. For sites to get to the VPC VLANS, they'd route over VLAN 511 to an HSRP VIP on the 5596's.

I have not decided whether I should port-channel the 4900s together or not yet in this design, letting RSTP block what is needed. Comments on that line?

Thoughts?

1 REPLY
New Member

Nexus 5596/2248 pair with 4900M pair

.....and would it really just be better to make 2 L3 PTP "no switchport" links per switch and have 4 ECMP links? We really like to be able to trunk a few VLANs system wide and going L3 kills this.

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