Default routing (not on blueprint)

General information on “Default routing”:

• A default route is a route, where all traffic not matching any other, more specific prefix, goes to
• IPv4 default route: 0.0.0.0/0
• IPv6 default route: ::/0

Static default doute

General information on “Static default route”:

• The target of the default route should be the next-hop IP address (exit-interface only is possible but not recommended)
• If the next-hop is an IPv6 link-local address, then a exit-interface is mandatory
• By default, the AD for a statically configured route is 1 but can be changed

“Static default route” CLI configuration commands:

## Configuring a static IPv4 default route
Router(config-router)# ip route 0.0.0.0 0.0.0.0 [<next-hop-ip> | <exit-if>] [<ad>]

## Configuring a static IPv6 default route
Router(config-router)# ipv6 route ::/0 [<next-hop-ip> | <exit-if>] [<ad>]

EIGRP default route

In EIGRP there are two ways:

1. Static route + redistribution/network command:
   • Configure a static default route
   • Inject the route via redistribution (IPv4 + IPv6) or the network command (IPv4 only)
2. Summary-address:
   • In EIGRP classic mode: Configured on the interface running EIGRP
   • In EIGRP named mode: Configured under the af-interface within the EIGRP process

“EIGRP default route” CLI configuration commands:

## Configuring an EIGRP default route using redistribution (classic mode)
Router(config)# ip route 0.0.0.0 0.0.0.0 [<next-hop-ip> | <exit-if>] [<ad>]
Router(config-router)# redistribute static metric [metric parameters]

## Configuring an EIGRP default route using the network command (classic mode)
Router(config)# ip route 0.0.0.0 0.0.0.0 [<next-hop-ip> | <exit-if>] [<ad>]
Router(config-router)# network 0.0.0.0 0.0.0.0

## Configuring an EIGRP default route using redistribution (named mode)
Router(config)# ip route 0.0.0.0 0.0.0.0 [<next-hop-ip> | <exit-if>] [<ad>]
Router(config-router-af-topology)# redistribute static metric [metric parameters]

## Configuring an EIGRP default route using the network command (named mode)
Router(config)# ip route 0.0.0.0 0.0.0.0 [<next-hop-ip> | <exit-if>] [<ad>]
Router(config-router-af-topology)# network 0.0.0.0 0.0.0.0

## Configuring an EIGRP default route using the summary-address (classic mode)
Router(config-if)# ip summary-address eigrp <asn> 0.0.0.0 0.0.0.0

## Configuring an EIGRP default route using the summary-address (named mode)
Router(config-router-af-interface)# summary-address 0.0.0.0 0.0.0.0

OSPF default route

General information about “OSPF default route”:

• Default Route injection is done on ASBRs
• The route will be injected as E2 route (Type 5 LSA)
• Without additional parameters, the route must exist in the routing table already
• If the parameter always is used, it will be advertised even if it doesn’t exist yet
• Unlike in EIGRP, it’s not possible to redistribute a default route
• Important: Within an NSSA a different command must be used to inject the default route as a Type 7 LSA!

## Injecting an OSPF default route within normal areas
Router(config)# router ospf <pid>
Router(config-router)# default-information-originate [always | metric | metric-type | route-map]

## Injecting an OSPF default route within a NSSA
Router(config)# router ospf <pid>
Router(config-router)# area <id> nssa default-information-originate [metric | metric-type | route-map | nssa-only | ...]

BGP default route

In BGP there are three ways:

1. Using the network command:
   • The default route must be in the routing table
   • Can be configured globally
2. Using redistribution:
   • The default route must be in the routing table and learned by the protocol redistributing from
   • Can be configured globally
3. Using unconditional origination:
   • The default route must not be in the routing table
   • Can be configured on a per-neighbor basis

“BGP default route” CLI configuration commands:

## Configuring a BGP default route using the network command
Router(config)# router bgp <asn>
Router(config-router)# address-family [ipv4 | ipv6 | vpnv4 | ...]
Router(config-router-af)# network 0.0.0.0

## Configuring a BGP default route using redistribution
Router(config)# router bgp <asn>
Router(config-router)# address-family [ipv4 | ipv6 | vpnv4 | ...]
Router(config-router-af)# redistribute <protocol>
Router(config-router-af)# default-information originate

## Configuring an unconditional BGP default route on a per-neighbor basis
Router(config)# router bgp <asn>
Router(config-router)# address-family [ipv4 | ipv6 | vpnv4 | ...]
Router(config-router-af)# neighbor <ip> default-originate