BGP Commands

Question 1

Command to initialize the BGP Process?

Answer 1

Router(config)# router bgp as-number

Question 2

Identify a BGP peer to establish a neighbor session

Answer 2

Router(config-router)# neighbor ip-address remote-as AS-number

Question 3

Disable the automatic ipv4 address-family configuration mode in BGP.

Answer 3

Router(config-router)# no bgp default ipv4-unicast

Question 4

Initialize a specific address-family and sub-address family configuration mode

Answer 4

Router(config-router)# address-family afi safi

Example:
Router(config-router)# address-family ipv6 unicast
Router(config-router-af)#

Question 5

Make a BGP neighbor active for a specific address-family

Answer 5

Router(config-router-af)# neighbor ip-address activate

Note: from address-family configuration mode.

Question 6

Advertise a network to BGP

Answer 6

Router(config-router)# network network mask subnet-mask [route-map route-map-name]

Example: Router(config-router)# network 10.9.8.0 mask 255.255.255.0 route-map RM_BGP_ROUTES

Question 7

Configure a BGP aggregate IPv4 prefix (summary)

Answer 7

Router(config-router-af)# aggregate-address network subnet-mask [summary-only] [as-set]

Example: Router(config-router)# aggregate-address 10.9.8.0 255.255.255.0 summary-only as-set

NOTE: If bgp default ipv4-unicast is disabled, this is done in address-family config mode

Question 8

Configure a BGP aggregate IPv6 prefix (summary)

Answer 8

Router(config-router-af)# aggregate-address prefix/prefix-length [summary-only] [as-set]

Example: Router(config-router)# aggregate-address 2001:db8:23:a/64 summary-only as-set

Question 9

Display the contents of the BGP database

Answer 9

Router# show bgp afi safi [network] [detailed]

Example: Router# show bgp ipv4 unicast 10.9.8.0 detailed

Question 10

Display a summary of the BGP table and neighbor peering sessions

Answer 10

Router# show bgp afi safi summary

Example: Router# show bgp ipv4 unicast summary

Question 11

Display the negotiated BGP settings for a specified peer and the number of prefixes exchanged with that peer.

Answer 11

Router# show bgp afi safi neighbors ip-address

Example: Router# show bgp ipv4 unicast neighbors 10.4.4.1

Question 12

Display the Adj-RIB-Out BGP table for a specific BGP neighbor

Answer 12

Router# show bgp afi safi neighbors ip-address advertised-routes

Example: Router# show bgp ipv4 unicast neighbors 10.4.4.1 advertised routes

Question 13

What command is used on a BGP router to see the BGP peering state?

Answer 13

show tcp brief

Question 14

What command might you need to ensure that an iBGP neighbor a reachable next hop address so the route will get installed to the Global routing table?

Answer 14

Router(config-router)# neighbor ip-address next-hop-self

NOTE: This is configured in address-family mode when bgp default ipv4-unicast is disabled

Question 15

What command shows the BGP routing table?

Answer 15

show bgp afi safi

Example: show bgp ipv4 unicast

Question 16

What command would you use to ‘reset’ all bgp neighbors? Why do you need to be careful about using that command?

Answer 16

Router# clear ip bgp *

This command will break all connections to BGP peers until the neighbor states are reestablished.

Question 17

What is the command you would use to see all the routes being sent out from the router you are on?

Answer 17

show bgp AFI SAFI neighbors ip-address advertised-routes

Question 18

For iBGP, when configuring neighbors using loopback addresses, what additional command is needed?

Answer 18

Router(config-router)# neighbor ip-address update-source loopback-#

Example: Router(config-router)# neighbor 5.5.5.5 update-source loopback0

Question 19

What is the command to create a route map? (Include the common options)

Answer 19

Router(config)# route-map NAME [permit | deny] [sequence-number]

NOTE: Best practice is to start sequence numbers at 10 and increase by increments of 10 similar to an access-list.

Question 20

What is the command to create an AS-Path Access List?

Answer 20

Router(config)# ip as-path access-list number {permit | deny} regular-expression-string

Question 21

What is the command to create a prefix-list?

Answer 21

Router(config)# {ip | ipv6} prefix-list NAME [seq sequence-num] {permit | deny} network-address/netmask [ge value] [le value]

Example: ip prefix-list deny FILTER_1 seq 10 deny 1.1.1.0/24 ge 32

Question 22

What is the command to create a BGP community-list for the purpose of conditional route matching?

Answer 22

Router(config)# ip community-list {1-500 | standard list-name | expanded list-name} {permit | deny} community-pattern

Question 23

From route-map config mode, what is the command to match on a BGP AS-Path?

Answer 23

Router(config-route-map)# match as-path acl-number

Question 24

From route-map config mode, what is the command to match on IP addresses that was set in an ACL?

Answer 24

Router(config-route-map)# match ip address {acl-number | acl-name}

Question 25

What is the command to redistribute routes from an iGP into BGP without any route filtering?

Answer 25

Router(config-router)# **redistribute** *protocol-name* [*process-id*] NOTE: To redistribute from an IGP into BGP, this will be done in BGP configuration mode. When using address-families, it is done in the address-family config mode under the BGP process.

Question 26

What is the command to redistribute routes from an iGP into BGP using a route-map to filter the routes?

Answer 26

Router(config-router)# **redistribute** *protocol-name* [*process-id*] **subnets route-map** *RM-NAME* NOTE: To redistribute from an IGP into BGP, this will be done in BGP configuration mode. When using address-families, it is done in the address-family config mode under the BGP process.

Question 27

What is the command to see a BGP rib-failure reason when seen in a routing table?

Answer 27

**show bgp** *afi safi* **rib-failure** OR **show ip bgp rib-failure**

Question 28

When trying to configure an eBGP peer using loopback addresses, what two commands may be needed to ensure the default TTL for eBGP does not prevent peering?

Answer 28

Router(config-router)# **neighbor** *ip-address* **disable-connect-check** Router(config-router)# **neighbor** *ip-address* **ebgp-multihop** *1-255*

Question 29

What is the command to create a Route Reflector?

Answer 29

Router(config-router-af)# **neighbor** *ip-address* **route-reflector-client** NOTE: The command is done on the Route Reflector and in address-family config mode if applicable

Question 30

What are the commands to put a router into a BGP confederation?

Answer 30

Router(config)# **router bgp** *Member-AS-number* Router(config-router)# **bgp confederation identifier** *Main-AS-Number*

Question 31

What command specifies the router will peer with another Member-AS other than its own?

Answer 31

Router(config-router)# **bgp confederation peers** *Other-Member-AS*

Question 32

Hard reset a BGP session with a peer

Answer 32

Router# **clear bgp ipv4 unicast** *neighbor-ip*

Question 33

Soft reset a BGP session with a peer

Answer 33

Router# **clear bgp ipv4 unicast** *neighbor-ip* [in | out | soft]

Question 34

Show bgp routes that only include a specific AS in the AS Path

Answer 34

Router# **show bgp ipv4 unicast regexp** *regex-expression*

Question 35

What is the command to create a Route Map?

Answer 35

Router(config)# **route-map** *NAME* {**permit | deny**} [*sequence-num*]

Question 36

Inside a Route Map, match ip on a prefix-list

Answer 36

Router(config-route-map)# **match ip address prefix-list** *NAME*

Question 37

Inside a Route Map, set the weight attribute

Answer 37

Router(config-route-map)# **set weight** *value*

Question 38

Enable IPv6 on a router (before configuring BGP for IPv6)

Answer 38

Router(config)# **ipv6 unicast-routing**

Question 39

Create an IPv6 neighbor (4 commands)

Answer 39

Router(config)# router bgp *AS-number* Router(config-router)# neighbor *ipv6-address* remote-as *AS-number* Router(config-router)# address-family ipv6 unicast Router(config-router-af)# neighbor *ipv6-address* activate