Enterasys Networks X-PeditionTM manual Routing Table Manager & Secondary IP, Ospf & Secondary IP

General IP Features

Routing Table Manager & Secondary IP

If the interface is up, each primary and secondary IP address will have an entry in the routing table as a directly connected route. If the interface is rejected or the IP addresses configured on it are removed, the Routing Table Manager (RTM) will delete corresponding table route entries.

If any IP address - primary and secondaries - is deleted or changed, any static route based on the next hop reachable through that IP address will be removed from the active routing table. And if the IP address is restored, any static route removed earlier will be restored in the active table.

OSPF & Secondary IP

In OSPF, HELLO messages use the primary IP address as the source address. Adjacencies are set up based on the primary IP address only. Designated routers (DR) and back-up DRs use the primary IP as their IP addresses. The virtual link uses the primary IP only, as well.

OSPF can be enabled on primary and secondary IP addresses but should be enabled on the primary first. Also, if OSPF is used for routing, all OSPF-enabled secondary addresses of an interface should be configured in the same OSPF area as the primary address to function properly.

OSPF can be selectively enabled on a secondary IP address as long as it is already enabled on the primary IP address.

RIP & Secondary IP

If RIP is used for routing, route updates should be multicast or broadcast to each subnet represented by both the primary and secondary IP addresses.

If an interface is configured with a secondary IP address and split horizon is enabled, route updates learned from one specific network cannot be sent back to the same physical network. Only one routing update is sourced per network number if split horizon is disabled.

RIP can be selectively enabled on primary and secondary IP addresses.

Unnumbered Interface & Secondary IP

If an unnumbered interface attempts to borrow an IP address from an Ethernet interface upon which a secondary IP address is configured, only the primary IP address can be borrowed. Also, secondary IP cannot be configured on an unnumbered interface.

NAT & Secondary IP

Only the primary IP address on the specified interface is used for NAT.

DHCP & Secondary IP

DHCP operates in the same manner regardless if secondary IP addresses are configured or not. Only one IP pool is employed even if multiple IP addresses are configured on a single interface.

VPN & Secondary IP

Secondary IP addresses are not supported on VPN virtual interfaces.

Concerning secondary IP addresses assigned to physical interfaces, if an interface constitutes the endpoint of a VPN tunnel, the primary IP address is always used as that tunnel endpoint. For the trusted interface upon which EZ-IPSec Network Extension Mode is running, only the SPD for the primary IP address assigned to the internal interface will be created.

XSR User’s Guide 5-9