Dell EMC S4128 pair - needs single ip gateways for vlans?

Hi.

Thank you for your question. The core issue is that the Dell N3024 switches supported stacking, which meant both switches acted as a single logical unit with one control plane, so a single gateway IP per VLAN just worked. The S4128 switches use VLT instead of stacking, meaning each switch maintains its own independent control plane. That is why a single shared gateway IP does not work out of the box.

There are two complementary features in OS10 that solve this problem. The first and most straightforward is VRRP, which stands for Virtual Router Redundancy Protocol. VRRP allows both switches to share a single virtual IP address on each VLAN, and that virtual IP is what all hosts use as their default gateway. One switch acts as the primary and the other as the backup, but the virtual IP remains the same regardless of which switch is handling traffic. This gives the customer exactly what they had before, a single gateway IP per VLAN, without needing to involve the ISP or make changes on the Juniper routers.

The second feature is VLT Peer Routing, which the customer already found referenced in the Anthony Critelli article. Yes, this concept does apply to OS10, not just FTOS. Peer routing is enabled within the VLT domain configuration and allows both VLT peers to route traffic on behalf of each other. When combined with VRRP, this means both switches can actively forward routed traffic rather than having to hairpin it across the VLTi link to whichever switch owns the VRRP primary role. This improves efficiency and performance.

The recommended approach would be to configure VRRP on each VLAN interface across both S4128 switches, assigning each switch a unique real IP on the VLAN and then a shared virtual IP that becomes the gateway for hosts. Then enable peer routing in the VLT domain configuration so both peers can actively route. The Juniper routers and downstream hosts would only ever see the single virtual gateway IP, so no changes should be needed on the ISP side.

The customer should consult the Dell OS10 Enterprise Edition User Guide for their specific firmware version, as it contains the exact CLI syntax for both VRRP and VLT peer routing configuration. Dell Support can also assist with validation of the configuration before it goes into production if needed.

Let us know if you have any other questions.

@DELL-Josh Cr​ 

Thank you for the response, I had come accross VRRP but one document recommended using Peer-routing only, using the same VLAN IP on both switches.  I tried to put the switches into production this morning but I got an odd issue - my Nutanix vlan 111 (Production) could not be contacted, but my second cluster (staging) vlan 1111 could.  Other vlans residing on the clusters were accessible.  I also could not get traffic to go to the DMZ porrt on the Juniper.  Who do I need to contact to get the configs checked?

Many thanks

Eric

You will need to contact phone support. Support Home | Dell US If you put in your service tag it should give you the right number.