Cisco Nexus 5500 Series NX-OS Unicast Routing Command Reference

N Commands

This chapter describes the Cisco NX-OS Border Gateway Protocol (BGP) commands that begin with N.

neighbor

To configure a Border Gateway Protocol (BGP) neighbor (router or VRF) and enter the neighbor configuration mode, use the neighbor command. To remove an entry, use the no form of this command.

neighbor {ip-addr | ip-prefix/length} [remote-as {as-num[.as-num] | route-map name}

no neighbor {ip-addr | ip-prefix/length} [remote-as {as-num[.as-num] | route-map name}]

Syntax Description

Command Default

None

Command Modes

Command HistoryNeighbor address-family configuration mode
Router bgp configuration mode

Usage Guidelines

From the BGP neighbor configuration mode, you can perform the following actions:

•address-family—Configures an address-family (router, neighbor, VRF). See the address-family (BGP) command for information.

•description description—Describes the neighbor. You can enter up to 80 characters including spaces.

•disable-connected-check—Disables the connection verification for the directly connected peer. Use the disable-connected-check command to disable a check for an exterior Border Gateway Protocol (eBGP) peer that is directly connected to the local router. BGP triggers a connection check automatically for all eBGP peers that are known to be a single hop away, unless you disable this check with the disable-connected-check command. BGP does not bring up sessions if the check fails. BGP considers an EBGP peer as a single hop away if the eBGP peer does does not have the ebgp-multihop command configured (that is, the time-to-live (TTL) value is one).

This command is ignored if the route-map keyword is used in the neighbor command.

•dont-capability-negotiate—Turns off the negotiate capability with this neighbor.

•dynamic-capability—Enables the dynamic capability.

•ebgp-multihop—Accepts and attempts BGP connections to external peers that reside on networks that are not directly connected. This command is ignored if the route-map keyword is used in the neighbor command.

Note You should enter this command under the guidance of Cisco technical support staff only.

•exit—Exits from the current command mode.

•inherit peer-session session-name—Configures a peer to inherit the configuration from another peer-session template. To remove an inherit statement from a peer-session template, use the no form of this command.

•no—Negates a command or sets its defaults.

•transport connection-mode passive—Allows a passive connection setup only. To remove the restriction, use the no form of this command.

•remove-private-as—Removes the private AS number from the outbound updates.

•shutdown—Administratively shuts down this neighbor.

•timers keepalive-time—Configures keepalive and hold timers in seconds. The range is from 0 to 3600. The default is 60.

•update-source {ethernet mod/port | loopback virtual-interface | port-channel number[.sub-interface]}—Specifies the source of the BGP session and updates. The range for virtual-interface is from 0 to 1023. The range for number is from 0 to 4096. The range for sub-interface is from 1 to 4093.

The Cisco NX-OS software allows BGP sessions to use any operational interface for TCP connections when you enter the update-source command in neighbor configuration mode. To restore the interface assignment to the closest interface, which is called the best local address, use the no form of this command.

This command requires the LAN Enterprise Services license.

Examples

This example shows how to configure a single-hop eBGP peering session between two BGP peers that are reachable on the same network segment through a local loopback interfaces on each router:

BGP Peer 1

switch(config)# interface loopback 1

switch(config-if)# ip address 10.0.0.100 255.255.255

switch(config-if)# exit

switch(config)# router bgp 64497

switch(config-router)# neighbor 192.168.0.200 remote-as 64496

switch(config-router-neighbor)# update-source loopback 2

switch(config-router-neighbor)# disable-connected-check

switch(config-router-neighbor)#

BGP Peer 2

switch(config)# interface loopback 2

switch(config-if)# ip address 192.168.0.200 255.255.255

switch(config-if)# exit

switch(config)# router bgp 64496

switch(config-router)# neighbor 10.0.0.100 remote-as 64497

switch(config-router-neighbor)# update-source loopback 1

switch(config-router-neighbor)# disable-connected-check

switch(config-router-neighbor)#

This example shows how to source BGP TCP connections for the specified neighbor with the IP address of the loopback interface rather than the best local address:

switch(config)# router bgp 64496

switch(config-router)# neighbor 172.16.0.0 remote-as 64496

switch(config-router-neighbor)# update-source Loopback0

switch(config-router-neighbor)#

Related Commands

network

To configure an IP prefix to advertise, use the network command. To remove the IP prefix to advertise, use the no form of this command.

network ip-addr | ip-prefix/length mask mask-num [route-map name]

no network ip-network | ip-prefix/length mask mask-num [route-map name]

Syntax Description

Command Default

None

Command Modes

Command HistoryNeighbor address-family configuration mode
Router bgp configuration mode

Usage Guidelines

The IP prefix to advertise is considered as a best path and advertisement to peers only if a route of equal or more specificity is present in the routing table.

Examples

This example shows how to configure an IP prefix to advertise:

switch(config-router-af)# network 2.2.2.2 mask 3.3.3.3 route-map test

switch(config-router-af)#

Related Commands

nexthop route-map

To specify that Border Gateway Protocol (BGP) routes are resolved using only the next hops that have routes that match specific characteristics, use the nexthop route-map command. To remove the route map, use the no form of this command.

nexthop route-map name

no nexthop route-map name

Syntax Description

Command Default

None

Command Modes

Command HistoryAddress-family configuration mode

Usage Guidelines

Use the nexthop route-map command to configure route policy filtering for next hops.

BGP next-hop filtering allows you to specify that when a next-hop address is checked with the Routing Information Base (RIB), the underlying route for that next-hop address is passed through the route map. If the route map rejects the route, the next-hop address is treated as unreachable.

BGP marks all next hops that are rejected by the route policy as invalid and does not calculate the best path for the routes that use the invalid next-hop address.

This command requires an LAN Enterprise Services license.

Examples

This example shows how to configure a route map to filter the next-hop address:

switch# configure terminal

switch(config)#route-map CHECK-BGP25 deny 10

switch(config-route-map)# match ip address prefix-list FILTER25

switch(config-route-map)# match source-protocol ospf-o1

switch(config-route-map)# exit

switch(config)#ip prefix-list FILTER25 seq 5 permit 0.0.0.0/0 le 25

switch(config)# router bgp 1.0

switch(config-router)# address-family ipv4 unicast

switch(config-router-af)# nexthop route-map CHECK-BGP25

switch(config-router-af)#

Related Commands

next-hop-self

To set the IP address of the router as the next hop address, use the next-hop-self command. To revert to the default configuration, use the no form of this command.

next-hop-self

no next-hop-self

Syntax Description

This command has no arguments or keywords.

Command Default

None

Command Modes

Command HistoryBGP neighbor address-family configuration mode

Usage Guidelines

This command requires a LAN Enterprise Services license.

Examples

This example shows how to configure the IP address of a router as the next-hop address:

switch# configure terminal

switch(config)# router bgp 102

switch(config-router)# neighbor 192.168.1.3 remote-as 64497

switch(config-router-neighbor)# address-family ipv4 unicast

switch(config-router-neighbor-af)# next-hop-self

switch(config-router-neighbor-af)#

Related Commands

nexthop trigger-delay

To specify a Border Gateway Protocol (BGP) delay for triggering next-hop calculations, use the nexthop trigger-delay command. To set the trigger delay to the default value, use the no form of this command.

nexthop trigger-delay {critical delay | non-critical delay}

no nexthop trigger-delay {critical delay | non-critical delay}

Syntax Description

Command Default

Critical delay: 3000 milliseconds.
Noncritical delay: 10000 milliseconds.

Command Modes

Command HistoryAddress-family configuration mode

Usage Guidelines

Use the nexthop trigger-delay command to modify when BGP processes next-hop address tracking events.

The non-critical delay value must always be set to a value that is at least equal or greater to the critical delay value.

The delay should be slightly higher than the time it takes for the Interior Gateway Protocol (IGP) to settle into a steady state after some event (IGP convergence time).

This command requires a LAN Enterprise Services license.

Examples

This example shows how to modify the next-hop address tracking delay:

switch# configure terminal

switch(config)# router bgp 1.0

switch(config-router)# address-family ipv4 unicast

switch(config-router-af)# nexthop trigger-delay critical 5000 non-critical 20000

Related Commands