Administrator Guide

VLT Proxy Gateway

Proxy Gateway in VLT Domains

Using a proxy gateway, the VLT peers in a domain can route the L3 packets destined for VLT peers in another domain as long as they

have L3 reachability for the IP destinations.

A proxy gateway in a VLT domain provides the following benefits:

• Avoids sub-optimal routing of packets by a VLT domain when packets are destined to the endpoint in another VLT domain.

• Provides resiliency if a VLT peer goes down by performing proxy routing for the peer’s destination MAC address in another VLT

domain.

A typical scenario is virtual movement of servers across data centers as shown in Topology 1. Virtual movement enables live migration of

running Virtual Machines (VMs) from one host to another without a downtime. Consider a square VLT connecting two data centers.

If a VM has for example the following scenario, L3 packets destined for C can be routed either by C1 or D1 locally:This behavior is achieved

by installing the local system mac address of C and D in both C1 and D1 so the packets for C and D could have a hit at C1 /D1 and be

routed locally.

• VM1 on Server Rack 1 has C as its default gateway

• VM1 performs a virtual movement to Server Rack 2 with no change in default gateway,

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 Link Aggregation Group

(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.

Similarly, C1 and D1 are Layer 3 core routers in DC2, in which VLT routing is enabled. The core routers C and D in the local VLT domain are

connected to the core routers C1 and D1 in the remote VLT Domain using VLT links in eVLT fashion. For more information about the eVLT,

see the Virtual Link Trunking (VLT) chapter. The core or Layer 3 routers C and D in local VLT Domain and C1 and D1 in the remote VLT

Domain are then part of a Layer 3 cloud.

946 VLT Proxy Gateway