Split Horizon; Poison Reverse; Triggered Updates; Route Advertisement Of Vlans - Extreme Networks ExtremeWare XOS Guide Manual

Route Redistribution

Split Horizon

Split horizon is a scheme for avoiding problems caused by including routes in updates sent to the
router from which the route was learned. Split horizon omits routes learned from a neighbor in updates
sent to that neighbor.

Poison Reverse

Like split horizon, poison reverse is a scheme for eliminating the possibility of loops in the routed
topology. In this case, a router advertises a route over the same interface that supplied the route, but the
route uses a hop count of 16, which defines that router as unreachable.

Triggered Updates

Triggered updates occur whenever a router changes the metric for a route. The router is required to
send an update message immediately, even if it is not yet time for a regular update message to be sent.
This generally results in faster convergence, but may also result in more RIPng-related traffic.

Route Advertisement of VLANs

Virtual LANs (VLANs) that are configured with an IP address but are configured to not route IP or are
not configured to run RIP, do not have their subnets advertised by RIP. RIP advertises only those
VLANs that are configured with an IP address, are configured to route IP, and run RIP.
Route Redistribution
More than one routing protocol can be enabled simultaneously on the switch. Route redistribution
allows the switch to exchange routes, including static routes, between the routing protocols. Route
redistribution is also called route export.

Configuring Route Redistribution

Exporting routes from one protocol to another and from that protocol to the first one are discreet
configuration functions. For example, to run OSPFv3 and RIPng simultaneously, you must first
configure both protocols and then verify the independent operation of each. Then you can configure the
routes to export from OSPFv3 to RIPng and the routes to export from RIPng to OSPFv3. Likewise, for
any other combinations of protocols, you must separately configure each to export routes to the other.
Redistributing Routes into RIPng
Enable or disable the exporting of static, direct, or other protocol-learned routes into the RIPng domain
using the following commands:
enable ripng export [direct | ospfv3 | ospfv3-extern1 | ospfv3-extern2 | ospfv3-
inter | ospfv3-intra | static] [cost <number> {tag <number>} | policy <policy-name>]
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ExtremeWare XOS 11.3 Concepts Guide