BGP Basic Configuration Example [ Step by step]
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Topology
BGP Configuration
R1 Configuration:
R1#show run
Building configuration...
Current configuration : 799 bytes
version 15.4
hostname R1
interface Loopback0
ip address 1.1.1.1 255.255.255.255
!
interface GigabitEthernet0/0/0
ip address 8.8.8.1 255.255.255.0
duplex auto
speed auto
!
router bgp 65001
bgp log-neighbor-changes
no synchronization
neighbor 8.8.8.2 remote-as 65002
network 8.8.8.0 mask 255.255.255.0
network 1.1.1.1 mask 255.255.255.255
R2 Configuration:
R2#show running-config
Building configuration...
Current configuration : 846 bytes
!
version 15.4
no service timestamps log datetime msec
no service timestamps debug datetime msec
no service password-encryption
!
hostname R2
!
ip cef
no ipv6 cef
spanning-tree mode pvst
interface Loopback0
ip address 2.2.2.2 255.255.255.255
!
interface GigabitEthernet0/0/0
ip address 8.8.8.2 255.255.255.0
duplex auto
speed auto
!
router bgp 65002
bgp log-neighbor-changes
no synchronization
neighbor 8.8.8.1 remote-as 65001
network 2.2.2.2 mask 255.255.255.255
network 8.8.8.0 mask 255.255.255.0
network 15.1.1.0 mask 255.255.255.0BGP peering Verifications
- Show ip bgp neighbor:
R1:
R1#show ip bgp neighbors
BGP neighbor is 8.8.8.2, remote AS 65002, external link
BGP version 4, remote router ID 2.2.2.2
BGP state = Established, up for 00:47:17
Last read 00:47:17, last write 00:47:17, hold time is 180, keepalive interval is 60 seconds
Neighbor capabilities:
Route refresh: advertised and received(new)
Address family IPv4 Unicast: advertised and received
Message statistics:
InQ depth is 0
OutQ depth is 0
Sent Rcvd
Opens: 1 1
Notifications: 0 0
Updates: 3 3
Keepalives: 48 48
Route Refresh: 0 0
Total: 52 52
Default minimum time between advertisements runs is 30 seconds
For address family: IPv4 Unicast
BGP table version 6, neighbor version 6/0
Output queue size : 0
Index 1, Offset 0, Mask 0x2
1 update-group member
Sent Rcvd
Prefix activity: ---- ----
Prefixes Current: 3 3 (Consumes 138 bytes)
Prefixes total: 3 3
Implicit Withdraw: 0 0
Explicit Withdraw: 0 0
Used as bestpath: n/a 1
Used as multipath: n/a 0
Outbound Inbound
Local Policy Denied Prefixes: -------- -------
Total: 0 0
Number of NLRIs in the update sent: max 3, min 1
Address tracking is enabled, the RIB does have a route to 8.8.8.2
Connections established 1; dropped 3
Last reset never
Transport(tcp) path-mtu-discovery is enabled
Connection state is ESTAB, I/O status: 1, unread input bytes: 0
Connection is ECN Disabled, Minimum incoming TTL 0, Outgoing TTL 1
Local host: 8.8.8.1, Local port: 179
Foreign host: 8.8.8.2, Foreign port: 1025
Connection tableid (VRF): 0
Enqueued packets for retransmit: 0, input: 0 mis-ordered: 0 (0 bytes)
Event Timers (current time is 0xC69F4):
Timer Starts Wakeups Next
Retrans 0 0 0x0
TimeWait 0 0 0x0
AckHold 51 0 0x0
SendWnd 0 0 0x0
KeepAlive 48 0 0x0
GiveUp 0 0 0x0
PmtuAger 0 0 0x0
DeadWait 0 0 0x0
Linger 0 0 0x0
ProcessQ 0 0 0x0
iss: 2057115318 snduna: 2057115748 sndnxt: 2057115748 sndwnd: 15955
irs: 3480424370 rcvnxt: 3480424751 rcvwnd: 16004 delrcvwnd: 380
SRTT: 259 ms, RTTO: 579 ms, RTV: 320 ms, KRTT: 0 ms
minRTT: 16 ms, maxRTT: 300 ms, ACK hold: 200 ms
Status Flags: passive open, gen tcbs
Option Flags: nagle, path mtu capable
IP Precedence value : 6
Datagrams (max data segment is 1460 bytes):
Rcvd: 52 (out of order: 0), with data: 0, total data bytes: 0
Sent: 49 (retransmit: 0, fastretransmit: 0, partialack: 0, Second Congestion: 0), with data: 3, total data bytes: 72
Packets received in fast path: 0, fast processed: 0, slow path: 0
fast lock acquisition failures: 0, slow path: 0
R2:
R2#show ip bgp neighbors
BGP neighbor is 8.8.8.1, remote AS 65001, external link
BGP version 4, remote router ID 1.1.1.1
BGP state = Established, up for 00:48:42
Last read 00:48:42, last write 00:48:42, hold time is 180, keepalive interval is 60 seconds
Neighbor capabilities:
Route refresh: advertised and received(new)
Address family IPv4 Unicast: advertised and received
Message statistics:
InQ depth is 0
OutQ depth is 0
Sent Rcvd
Opens: 1 1
Notifications: 0 0
Updates: 3 3
Keepalives: 49 49
Route Refresh: 0 1
Total: 53 54
Default minimum time between advertisements runs is 30 seconds
For address family: IPv4 Unicast
BGP table version 6, neighbor version 6/0
Output queue size : 0
Index 1, Offset 0, Mask 0x2
1 update-group member
Sent Rcvd
Prefix activity: ---- ----
Prefixes Current: 3 2 (Consumes 115 bytes)
Prefixes total: 3 2
Implicit Withdraw: 0 0
Explicit Withdraw: 0 0
Used as bestpath: n/a 1
Used as multipath: n/a 0
Outbound Inbound
Local Policy Denied Prefixes: -------- -------
Total: 0 0
Number of NLRIs in the update sent: max 3, min 1
Address tracking is enabled, the RIB does have a route to 8.8.8.1
Connections established 1; dropped 0
Last reset never
Transport(tcp) path-mtu-discovery is enabled
Connection state is ESTAB, I/O status: 1, unread input bytes: 0
Connection is ECN Disabled, Minimum incoming TTL 0, Outgoing TTL 1
Local host: 8.8.8.2, Local port: 1025
Foreign host: 8.8.8.1, Foreign port: 179
Connection tableid (VRF): 0
Enqueued packets for retransmit: 0, input: 0 mis-ordered: 0 (0 bytes)
Event Timers (current time is 0xC69F4):
Timer Starts Wakeups Next
Retrans 0 0 0x0
TimeWait 0 0 0x0
AckHold 52 0 0x0
SendWnd 0 0 0x0
KeepAlive 49 0 0x0
GiveUp 0 0 0x0
PmtuAger 0 0 0x0
DeadWait 0 0 0x0
Linger 0 0 0x0
ProcessQ 0 0 0x0
iss: 2057115318 snduna: 2057115748 sndnxt: 2057115748 sndwnd: 15955
irs: 3480424370 rcvnxt: 3480424751 rcvwnd: 16004 delrcvwnd: 380
SRTT: 259 ms, RTTO: 579 ms, RTV: 320 ms, KRTT: 0 ms
minRTT: 16 ms, maxRTT: 300 ms, ACK hold: 200 ms
Status Flags: passive open, gen tcbs
Option Flags: nagle, path mtu capable
IP Precedence value : 6
Datagrams (max data segment is 1460 bytes):
Rcvd: 53 (out of order: 0), with data: 1, total data bytes: 24
Sent: 50 (retransmit: 0, fastretransmit: 0, partialack: 0, Second Congestion: 0), with data: 3, total data bytes: 72
Packets received in fast path: 0, fast processed: 0, slow path: 0
fast lock acquisition failures: 0, slow path: 0
R2#- Show ip BGP
R1#show ip bgp
BGP table version is 6, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 1.1.1.1/32 0.0.0.0 0 0 32768 i
*> 2.2.2.2/32 8.8.8.2 0 0 0 65002 i
*> 8.8.8.0/24 0.0.0.0 0 0 32768 i
* 8.8.8.2 0 0 0 65002 i
*> 15.1.1.0/24 8.8.8.2 0 0 0 65002 i
R1#
------------------------------------------------------------------------
R2#show ip bgp
BGP table version is 8, local router ID is 2.2.2.2
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 1.1.1.1/32 8.8.8.1 0 0 0 65001 i
*> 2.2.2.2/32 0.0.0.0 0 0 32768 i
*> 8.8.8.0/24 0.0.0.0 0 0 32768 i
* 8.8.8.1 0 0 0 65001 i
*> 15.1.1.0/24 0.0.0.0 0 0 32768 i- Show ip route:
R1#show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is not set
1.0.0.0/32 is subnetted, 1 subnets
C 1.1.1.1/32 is directly connected, Loopback0
2.0.0.0/32 is subnetted, 1 subnets
B 2.2.2.2/32 [20/0] via 8.8.8.2, 00:00:00
8.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 8.8.8.0/24 is directly connected, GigabitEthernet0/0/0
L 8.8.8.1/32 is directly connected, GigabitEthernet0/0/0
15.0.0.0/24 is subnetted, 1 subnets
B 15.1.1.0/24 [20/0] via 8.8.8.2, 00:00:00
------------------------------
R2# show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is not set
1.0.0.0/32 is subnetted, 1 subnets
B 1.1.1.1/32 [20/0] via 8.8.8.1, 00:00:00
2.0.0.0/32 is subnetted, 1 subnets
C 2.2.2.2/32 is directly connected, Loopback0
8.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 8.8.8.0/24 is directly connected, GigabitEthernet0/0/0
L 8.8.8.2/32 is directly connected, GigabitEthernet0/0/0
15.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 15.1.1.0/24 is directly connected, GigabitEthernet0/0/1
L 15.1.1.1/32 is directly connected, GigabitEthernet0/0/1