Users Guide

• The connection between DCs must be a L3 VLT in eVLT format . For more information, refer to the
eVLT Configuration Example
• The trace route across the DCs can show extra hops.
• To ensure no traffic drops, you must maintain route symmetry across the VLT domains. When the
routing table across DCs is not symmetrical, there is a possibility of a routing miss by a DC that does not
have the route for L3 traffic. Because routing protocols are enabled and both DCs are in the same
subnet, there is no dynamic route asymmetry. But if you configure a static route on one DC and not on
the other, there is asymmetry.
• If the port-channel specified in the proxy-gateway command is not a VLT LAG, the configuration is
rejected by the CLI.
• You cannot change the VLT LAG to a legacy LAG when it is part of proxy-gateway.
• You cannot change the link layer discovery protocol (LLDP) port channel interface to a legacy LAG when
you enable a proxy gateway.
• Dell Networking recommends the vlt-peer-mac transmit command only for square VLTs without
diagonal links.
• The virtual router redundancy (VRRP) protocol and IPv6 routing is not supported.
• Private VLANs (PVLANs) are not supported.
• When a Virtual Machine (VM) moves from one VLT domain to the another VLT domain, the VM host
sends the gratuitous ARP (GARP) , which in-turn triggers a mac movement from the previous VLT
domain to the newer VLT domain.
• After a station move, if the host sends a TTL1 packet destined to its gateway; for example, a previous VLT
node, the packet can be dropped.
• After a station move, if the host first PINGs its gateway; for example, a previous VLT node it results in a
40 to 60% success rate considering it takes a longer path.
• When you remove and add back a MAC address, L3 frames can be received out-of-order at the L3
cloud. This happens when proxy gateway routing and sub-optimal routing intersperse with each other.
Enabling the VLT Proxy Gateway
To enable the VLT proxy gateway, the system mac addresses of C and D in the local VLT domain must be
installed in C1 and D1 in the remote VLT domain and vice versa. You can install the mac address in two
methods - the proxy-gateway lldp method or the proxy-gateway static configuration. Proxy-
gateway LLDP is a dynamic method of installing the local mac addresses in the remote VLT domain, which is
achieved using a new organizational type, length, value (TLV) in LLDP packets.
You can configure the VLT proxy gateway in a VLT domain using the proxy-gateway LLDP command in
proxy-gateway Configuration mode. Specify the port-channel interface of the square VLT link on which LLDP
packets are sent using thepeer-domain-link port-channel command.
Configuring the proxy gateway lldp and the peer-domain-link port channel, LLDP sets TLV flags on
the interfaces for receiving and transmitting private TLV packets. After defining these organizational TLV
settings, LLDP encodes the local system mac-addresses as organizational TLVs for transmitting to the peer. If
you specify the no proxy gateway LLDP interface command, LLDP stops transmitting and receiving
proxy gateway TLV packets on the specified interfaces. However, other TLVs are not affected. From the
interfaces on which you enabled the proxy gateway LLDP, LLDP decodes the TLV packets from the remote
LLDP by using the new organizational TLV.
The following requirements must be satisfied for LLDP proxy gateway to function correctly:
• Data centers must be directly connected.
VLT Proxy Gateway 1022