Reference Guide

VLT Proxy Gateway

This chapter describes the VLT Proxy Gateway feature.

Proxy Gateway in VLT Domains

The functionality to configure the proxy gateway in VLT domains is supported on the S4810, S4820T,

S6000, Z9000 platforms.

You can configure a proxy gateway in VLT domains. A proxy gateway enables you to locally route the

packets that are destined to L3 endpoint of the other VLT domain. Therefore, the VLT peers of one

domain can route the L3 packets destined for VLT peers of another domain as long as they have

reachability for those IP destinations. This will avoid sub-optimal routing of sending the packets to the

actual VLT domain and routing them from there, in case the received packets are destined for the

endpoint of the other VLT domain. It also provides resiliency in case of VLT peer going down on one VLT

domain by performing the proxy routing for that peer’s DA MAC by the other VLT domain.

The typical scenario is virtual movement of servers across data centers. Virtual movement enables live

migration of running virtual machines from one host to another without a downtime. Consider a square

VLT connecting two data centers. If a VM, say VM1 on Server Rack 1 has C as its default gateway and VM1

performs a virtual movement to Server Rack 2 with no change in default gateway, then L3 packets

destined for C can be routed either C1 or D1 locally. This behavior is achieved by installing the local_DA

entries for C/D in C1/D1 so that the packets for C/D could have a hit at C1/D1 and routed locally.

In the following figure, server racks, named Rack 1 and Rack 2 are part of data centers, named DC1 and

DC2 respectively. Rack 1 is connected to devices A and B in Layer 2. Similarly, Rack 2 is connected to

devices A and B in Layer 2. A VLT LAG is present between A and B. A and B are connected to core routers,

C and D. VLT routing is present between C and D. C1 and D1 are Layer 3 routers in DC2 and they are

connected with core routers, C and D. The core or Layer 3 routers are then part of a Layer 3 cloud.

VLT Proxy Gateway

1019