Concept Guide

ip nexthop-list
ip nexthop-list <string>
ip {<ip-adddr>}|{dhcp vlan <id>} priority <0-255>
ipsec-map <name>
preemptive-failover
Description
Define a nexthop list for policy-based routing.
Syntax
Parameter Description
<name>
Name of the nexthop list
ip <ip-addr>
IP address of the nexthop device
ip dhcp vlan
<id>
VLAN ID of the VLAN used by the nexthop device. If the VLAN gets an IP address
using DHCP, and the default gateway is determined by the VLAN interface, the
gateway IP is used as the nexthop IP address.
ipsec-map <map_
name>
Packets can be redirected over a VPN tunnel by specifying the ipsec-map name.
preemptive-fail-
over
This column indicates whether preemptive failover is enabled or disabled.
If preemption is enabled and a higher priority nexthop becomes reachable again, pack-
ets are again forwarded to the higher priority nexthop.
Usage Guidelines
A nexthop IP is the IP address of a adjacent router or device with layer-2 connectivity to the controller. If the
controller uses policy-based routing to forwards packets to a nexthop device and that device becomes
unreachable, the packets matching the policy will not reach their destination. The Nexthop list provides
redundancy for the nexthop devices by forwarding the traffic to a backup nexthop device in case of failures. If
active nexthop device on the list becomes unreachable, traffic matching a policy-based routing ACL is
forwarded using the highest-priority active nexthop on the list.
A maximum of 4 nexthops can be added to a nexthoplist. Each nexthop can be assigned a priority, which
decides the order of selection of the nexthop. If a higher priority nexthop goes down, the next higher priority
nexthop which is active is chosen for forwarding. If all the nexthops are configured with same priority, the
order is determined based on the order in which they are configured. If all the nexthops are down, traffic is
passed regular destination based forwarding.
In a typical deployment scenario with multiple uplinks, the default route only uses one of the uplink next-hops
for forwarding packets. If a nexthop becomes unreachable, the packets will not reach their destination. If your
deployment uses policy-based routing based on a nexthop list, any of the uplink nexthops could be used for
forwarding traffic. This requires a valid ARP entry (route-cache) in the system for all the policy-based routing
nexthops.
In a branch controller deployment, the site uplinks can obtain their IP addresses and default gateway using
DHCP. In such deployments, the nexthop-list configuration can use the VLAN IDs of uplink VLANs. If the VLAN
gets an IP address using DHCP, and the default gateway is determined by the VLAN interface, the gateway IP is
Dell Networking W-Series ArubaOS 6.5.x | Reference Guide ip nexthop-list | 525