Brocade Communications Systems ICX 7250 series, Configuration Manual

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Treating missing MEDs as the worst MEDs
By default, the device favors a lower MED over a higher MED during MED comparison. Since the device assigns the value 0 to a route
path MED if the MED value is missing, the default MED comparison results in the device favoring the route paths that are missing their
MEDs.
To change this behavior so that the device favors a route that has a MED over a route that is missing its MED, enter the following
command at the BGP4 configuration level of the CLI.
device(config-bgp-router)# med-missing-as-worst
Syntax: [no] med-missing-as-worst
NOTE
This command affects route selection only when route paths are selected based on MED comparison. It is still possible for a
route path that is missing its MED to be selected based on other criteria. For example, a route path with no MED can be
selected if its weight is larger than the weights of the other route paths.
Configuring route reflection parameters
Normally, all the BGP4 devices within an AS are fully meshed. Since each device has an IBGP session with each of the other BGP4
devices in the AS, each IBGP device has a route for each IBGP neighbor. For large autonomous systems containing many IBGP devices,
the IBGP route information in each fully-meshed IBGP device may introduce too much administrative overhead.
To avoid this overhead, you can organize your IGP devices into clusters:
• A cluster is a group of IGP devices organized into route reflectors and route reflector clients. You configure the cluster by
assigning a cluster ID on the route reflector and identifying the IGP neighbors that are members of that cluster. All configuration
for route reflection takes place on the route reflectors. Clients are unaware that they are members of a route reflection cluster. All
members of the cluster must be in the same AS. The cluster ID can be any number from 1 - 4294967295, or an IP address.
The default is the device ID expressed as a 32-bit number.
NOTE
If the cluster contains more than one route reflector, you need to configure the same cluster ID on all the route reflectors in the
cluster. The cluster ID helps route reflectors avoid loops within the cluster.
• A route reflector is an IGP device configured to send BGP4 route information to all the clients (other BGP4 devices) within the
cluster. Route reflection is enabled on all BGP4 devices by default but does not take effect unless you add route reflector clients
to the device.
• A route reflector client is an IGP device identified as a member of a cluster. You identify a device as a route reflector client on the
device that is the route reflector, not on the client. The client itself requires no additional configuration. In fact, the client does not
know that it is a route reflector client. The client just knows that it receives updates from its neighbors and does not know
whether one or more of those neighbors are route reflectors.
NOTE
Route reflection applies only among IBGP devices within the same AS. You cannot configure a cluster that spans multiple
autonomous systems.
This is an example of a route reflector configuration. In this example, two devices are configured as route reflectors for the same cluster,
which provides redundancy in case one of the reflectors becomes unavailable. Without redundancy, if a route reflector becomes
unavailable, the clients for that device are cut off from BGP4 updates.
AS1 contains a cluster with two route reflectors and two clients. The route reflectors are fully meshed with other BGP4 devices, but the
clients are not fully meshed and rely on the route reflectors to propagate BGP4 route updates.
Optional BGP4 configuration tasks
Brocade FastIron Layer 3 Routing Configuration Guide
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