BGP

BGP AS-PATH Attributes

September 14, 2016 by

LAB2: BGP – IPv4

Disclaimer

This Configuration Guide is designed to assist members to enhance their skills in respective technology area. While every effort has been made to ensure that all material is as complete and accurate as possible, the enclosed material is presented on an “as is” basis. Neither the authors nor Forum assume any liability or responsibility to any person or entity with respect to loss or damages incurred from the information contained in this guide. This Lab Guide was developed by RSTForum. Any similarities between material presented in this configuration guide and any other material is completely coincidental.

LAB 2: Diagram

Note: This Lab was developed on Cisco IOS Version15.2(4) M1 ADVENTERPRISEK9-M.

LAB 2: Configure BGP AS-PATH Attributes:

Task 1: Configure BGP AS-PATH Attributes for Autonomous

In the configuration mode of router configure BGP AS-PATH Attributes by following command:

R1:

interface loopback 100

ip address 100.0.0.1 255.255.255.0

exit

router bgp 65100

address-family ipv4

network 100.0.0.0 mask 255.255.255.0

exit

R4:

interface loopback 100

ip address 100.0.0.4 255.255.255.0

exit

router bgp 65200

address-family ipv4

network 100.0.0.0 mask 255.255.255.0

exit

Verify IPv4 BGP routes by following command:

R2#show ip bgp

! (Shows router’s routing table and IPv4 routes entries)

BGP table version is 14, local router ID is 22.0.3.2

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,

x best-external, a additional-path, c RIB-compressed,

Origin codes: i - IGP, e - EGP, ? - incomplete

RPKI validation codes: V valid, I invalid, N Not found

Network Next Hop Metric LocPrf Weight Path

*> 11.0.1.0/24 11.0.1.1 0 0 65100 i

*> 11.0.2.0/24 11.0.1.1 0 0 65100 i

*> 11.0.3.0/24 11.0.1.1 0 0 65100 i

*> 22.0.1.0/24 0.0.0.0 0 32768 i

*> 22.0.2.0/24 0.0.0.0 0 32768 i

*> 22.0.3.0/24 0.0.0.0 0 32768 i

*>i 33.0.1.0/24 33.0.1.3 0 100 0 i

*>i 33.0.2.0/24 33.0.1.3 0 100 0 i

*>i 33.0.3.0/24 33.0.1.3 0 100 0 i

*>i 44.0.1.0/24 44.0.1.4 0 100 0 65200i

*>i 44.0.2.0/24 44.0.1.4 0 100 0 65200i

*>i 44.0.3.0/24 44.0.1.4 0 100 0 65200i

* i 100.0.0.0/24 44.0.1.4 0 100 0 65200i

*> 11.0.1.1 0 0 65100i

(R2 can reach 100 network via next hop 11.0.1.1 through AS 65100 and via 44.0.1.4 through AS 65200. Best path for R2 to reach 100 network is via next hop 11.0.1.1 because 11.0.1.1 is EBGP neighbor with AD value 20 and 44.0.1.4 is received from IBGP neighbor with AD value 200.)

Task 2: Configure BGP AS-PATH Manipulation for Autonomous

Prepend AS for as-path manipulation

! (Router R2 wants to make via 44.0.1.4 as best path instead of 11.0.1.1)

R2:

router bgp 65000

address-family ipv4

neighbor 11.0.1.1 route-map abc in

exit

route-map abc permit 10

set as-path prepend 222 22

exit

(A policy is call on Router R2 that 100 network is prepended 222 22 via 11.0.1.1 through AS 65100 222 22 i.e. through 3 AS)

R1:

router bgp 65100

address-family ipv4

neighbor 22.0.1.2 route-map abc out

exit

route-map abc permit 10

set as-path prepend 111 11

exit

(A policy is call on Router R1 that 100 network is prepended 111 11 via 11.0.1.1 through AS 111 11 65100 i.e. through 3 AS)

Verify IPv4 BGP routes by following command:

R2#show ip bgp

! (Shows router’s routing table and IPv4 routes entries)

BGP table version is 21, local router ID is 22.0.3.2

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,

x best-external, a additional-path, c RIB-compressed,

Origin codes: i - IGP, e - EGP, ? - incomplete

RPKI validation codes: V valid, I invalid, N Not found

Network Next Hop Metric LocPrf Weight Path

*> 11.0.1.0/24 11.0.1.1 0 0 22 22 65100 i

*> 11.0.2.0/24 11.0.1.1 0 0 222 22 65100 i

*> 11.0.3.0/24 11.0.1.1 0 0 222 22 65100 i

*> 22.0.1.0/24 0.0.0.0 0 32768 i

*> 22.0.2.0/24 0.0.0.0 0 32768 i

*> 22.0.3.0/24 0.0.0.0 0 32768 i

*>i 33.0.1.0/24 33.0.1.3 0 100 0 i

*>i 33.0.2.0/24 33.0.1.3 0 100 0 i

*>i 33.0.3.0/24 33.0.1.3 0 100 0 i

*>i 44.0.1.0/24 44.0.1.4 0 100 0 65200i

*>i 44.0.2.0/24 44.0.1.4 0 100 0 65200i

*>i 44.0.3.0/24 44.0.1.4 0 100 0 65200i

*>i 100.0.0.0/24 44.0.1.4 0 100 0 65200i

* 11.0.1.1 0 0 222 22 65100 i

(Router R2 now selects 44.0.1.4 as best path because it can reach 100 network through As 65200, where as to reach 100 network via 11.0.1.1 through AS 222 22 65100 111 11;Hence AS-PATH is manipulated.)

BGP Community String

September 14, 2016 by

LAB7: BGP – IPv4

Disclaimer

LAB 7: Diagram

Note: This Lab was developed on Cisco IOS Version15.2(4) M1 ADVENTERPRISEK9-M.

LAB 7: BGP Community String

Task 1: Configure IPv4 BGP Community String

In the configuration mode of router configure Community String Attributes by following command:

R1:

router bgp 65100

address-family ipv4

neighbor 22.0.1.2 send-community

neighbor 22.0.1.2 route-map aaa out

exit

route-map aaa permit 10

set community 8888

exit

Verify receipt of route in neighbor router’s by following command

R2#show ip bgp community

BGP table version is 13, local router ID is 22.0.3.2

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,

x best-external, a additional-path, c RIB-compressed,

Origin codes: i - IGP, e - EGP, ? - incomplete

RPKI validation codes: V valid, I invalid, N Not found

Network Next Hop Metric LocPrf Weight Path

*> 11.0.1.0/24 11.0.1.1 0 0 65100 i

*> 11.0.2.0/24 11.0.1.1 0 0 65100 i

*> 11.0.3.0/24 11.0.1.1 0 0 65100 i

R2#show ip bgp community 8888

BGP table version is 13, local router ID is 22.0.3.2

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,

x best-external, a additional-path, c RIB-compressed,

Origin codes: i - IGP, e - EGP, ? - incomplete

RPKI validation codes: V valid, I invalid, N Not found

Network Next Hop Metric LocPrf Weight Path

*> 11.0.1.0/24 11.0.1.1 0 0 65100 i

*> 11.0.2.0/24 11.0.1.1 0 0 65100 i

*> 11.0.3.0/24 11.0.1.1 0 0 65100 i

R2#show ip bgp 11.0.1.0

BGP routing table entry for 11.0.1.0/24, version 2

Paths: (1 available, best #1, table default)

Advertised to update-groups:

Refresh Epoch 1

65100, (received & used)

11.0.1.1 (metric 65) from 11.0.1.1 (11.0.3.1)

Origin IGP, metric 0, localpref 100, valid, external, best

Community: 8888

(11 network is tagged 8888 community.)

Task 2: Configure IPv4 BGP Community String Manipulation

In the configuration mode of router configure Community String Manipulation by following command:

R2:

router bgp 65000

address-family ipv4

neighbor 11.0.1.1 route-map bbb in

exit

ip community-list 1 permit 8888

route-map bbb permit 10

match community 1

set weight 9999

exit

Verify receipt of route in neighbor router’s bgp table by following command

R2#show ip bgp community

BGP table version is 16, local router ID is 22.0.3.2

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,

x best-external, a additional-path, c RIB-compressed,

Origin codes: i - IGP, e - EGP, ? - incomplete

RPKI validation codes: V valid, I invalid, N Not found

Network Next Hop Metric LocPrf Weight Path

*> 11.0.1.0/24 11.0.1.1 0 9999 65100 i

*> 11.0.2.0/24 11.0.1.1 0 9999 65100 i

*> 11.0.3.0/24 11.0.1.1 0 9999 65100 i

R2#show ip bgp

BGP table version is 16, local router ID is 22.0.3.2

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,

x best-external, a additional-path, c RIB-compressed,

Origin codes: i - IGP, e - EGP, ? - incomplete

RPKI validation codes: V valid, I invalid, N Not found

Network Next Hop Metric LocPrf Weight Path

*> 11.0.1.0/24 11.0.1.1 0 9999 65100 i

*> 11.0.2.0/24 11.0.1.1 0 9999 65100 i

*> 11.0.3.0/24 11.0.1.1 0 9999 65100 i

*> 22.0.1.0/24 0.0.0.0 0 32768 i

*> 22.0.2.0/24 0.0.0.0 0 32768 i

*> 22.0.3.0/24 0.0.0.0 0 32768 i

*>i 33.0.1.0/24 33.0.1.3 0 100 0 i

*>i 33.0.2.0/24 33.0.1.3 0 100 0 i

*>i 33.0.3.0/24 33.0.1.3 0 100 0 i

*>i 44.0.1.0/24 44.0.1.4 0 100 0 65200 i

*>i 44.0.2.0/24 44.0.1.4 0 100 0 65200 i

*>i 44.0.3.0/24 44.0.1.4 0 100 0 65200 i

(Policy is called to match only 8888 community and will change weight attribute to 9999. Hence manipulation is achieved with the help of Community String.)

BGP Initial Configuration

September 14, 2016 by

LAB1: BGP – IPv4

Disclaimer

LAB 1: Diagram

Note: This Lab was developed on Cisco IOS Version15.2(4) M1 ADVENTERPRISEK9-M.

LAB 1: Configure BGP FOR IPv4:

Task 1: Configure IPv4 BGP process for Autonomous

In the configuration mode of router configure IPv4 BGP Process by following cmd:

R1:

router bgp 65100 ! (Initiate BGP process for AS 65100)

neighbor 22.0.1.2 remote-as 65000 ! (Creates a BGP peer group)

neighbor 22.0.1.2 ebgp-multihop 5

neighbor 22.0.1.2 update-source loopback 1 ! (To form Loop to Loop indirect peering

neighbor 22.0.1.2 soft-reconfiguration inbound! (To store fresh incoming updated from

exit neighbor)

R2:

router bgp 65000

neighbor 11.0.1.1 remote-as 65100

neighbor 11.0.1.1 ebgp-multihop 5 ! (BGP connections to external peers

neighbor 11.0.1.1 update-source loopback 1 residing on networks that are not directly

neighbor 11.0.1.1 soft-reconfiguration inboundconnected.)

neighbor 33.0.1.3 remote-as 65000

neighbor 33.0.1.3 update-source loopback 1

neighbor 33.0.1.3 soft-reconfiguration inbound

exit

R3:

router bgp 65000

neighbor 22.0.1.2 remote-as 65000

neighbor 22.0.1.2 update-source loopback 1

neighbor 22.0.1.2 soft-reconfiguration inbound

neighbor 44.0.1.4 remote-as 65200

neighbor 44.0.1.4 ebgp-multihop 5

neighbor 44.0.1.4 update-source loopback 1

neighbor 44.0.1.4 soft-reconfiguration inbound

exit

R4:

router bgp 65200

neighbor 33.0.1.3 remote-as 65000

neighbor 33.0.1.3 ebgp-multihop 5

neighbor 33.0.1.3 update-source loopback 1

neighbor 33.0.1.3 soft-reconfiguration inbound

exit

In the configuration mode of router configure IPv4 OSPF Process by following command:

R1:

router ospf 1 ! (Initiate OSPF process with process id 1)

network 0.0.0.0 0.0.0.0 area 0 ! (Send updates on any ip with any mask)

exit

R2:

router ospf 1

network 0.0.0.0 0.0.0.0 area 0

exit

R3:

router ospf 1

network 0.0.0.0 0.0.0.0 area 0

exit

R4:

router ospf 1

network 0.0.0.0 0.0.0.0 area 0

exit

Announce the network in BGP Process

R1:

router bgp 65100

address-family ipv4 ! (Enable address family for IPv4 BGP)

network 11.0.1.0 mask 255.255.255.0 ! (Announce the network in BGP process)

network 11.0.2.0 mask 255.255.255.0

network 11.0.3.0 mask 255.255.255.0

exit

R2:

router bgp 65000

address-family ipv4

network 22.0.1.0 mask 255.255.255.0

network 22.0.2.0 mask 255.255.255.0

network 22.0.3.0 mask 255.255.255.0

exit

R3:

router bgp 65000

address-family ipv4

network 33.0.1.0 mask 255.255.255.0

network 33.0.2.0 mask 255.255.255.0

network 33.0.3.0 mask 255.255.255.0

exit

R4:

router bgp 65200

address-family ipv4

network 44.0.1.0 mask 255.255.255.0

network 44.0.2.0 mask 255.255.255.0

network 44.0.3.0 mask 255.255.255.0

exit

Task 2: Verification:

Verify IPv4 routes in routing table by following command:

R2#show ip route

! (Shows router’s routing table and IPv4 routes entries)

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

i - IS-IS, su - IS-IS summary, 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, H - NHRP, l - LISP

+ - replicated route, % - next hop override

Gateway of last resort is not set

11.0.0.0/8 is variably subnetted, 6 subnets, 2 masks

B 11.0.1.0/24 [20/0] via 11.0.1.1, 00:07:49

O 11.0.1.1/32 [110/65] via 12.0.0.1, 00:17:07, Serial2/0

B 11.0.2.0/24 [20/0] via 11.0.1.1, 00:07:19

O 11.0.2.1/32 [110/65] via 12.0.0.1, 00:17:07, Serial2/0

B 11.0.3.0/24 [20/0] via 11.0.1.1, 00:07:19

O 11.0.3.1/32 [110/65] via 12.0.0.1, 00:17:07, Serial2/0

12.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C 12.0.0.0/24 is directly connected, Serial2/0

L 12.0.0.2/32 is directly connected, Serial2/0

22.0.0.0/8 is variably subnetted, 6 subnets, 2 masks

C 22.0.1.0/24 is directly connected, Loopback1

L 22.0.1.2/32 is directly connected, Loopback1

C 22.0.2.0/24 is directly connected, Loopback2

L 22.0.2.2/32 is directly connected, Loopback2

C 22.0.3.0/24 is directly connected, Loopback3

L 22.0.3.2/32 is directly connected, Loopback3

23.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C 23.0.0.0/24 is directly connected, Ethernet0/0

L 23.0.0.2/32 is directly connected, Ethernet0/0

33.0.0.0/8 is variably subnetted, 6 subnets, 2 masks

B 33.0.1.0/24 [200/0] via 33.0.1.3, 00:04:04

O 33.0.1.3/32 [110/11] via 23.0.0.3, 00:16:08, Ethernet0/0

B 33.0.2.0/24 [200/0] via 33.0.1.3, 00:04:00

O 33.0.2.3/32 [110/11] via 23.0.0.3, 00:16:08, Ethernet0/0

B 33.0.3.0/24 [200/0] via 33.0.1.3, 00:03:56

O 33.0.3.3/32 [110/11] via 23.0.0.3, 00:16:08, Ethernet0/0

34.0.0.0/24 is subnetted, 1 subnets

O 34.0.0.0 [110/74] via 23.0.0.3, 00:16:08, Ethernet0/0

44.0.0.0/8 is variably subnetted, 6 subnets, 2 masks

B 44.0.1.0/24 [200/0] via 44.0.1.4, 00:03:03

O 44.0.1.4/32 [110/75] via 23.0.0.3, 00:16:08, Ethernet0/0

B 44.0.2.0/24 [200/0] via 44.0.1.4, 00:02:33

O 44.0.2.4/32 [110/75] via 23.0.0.3, 00:16:08, Ethernet0/0

B 44.0.3.0/24 [200/0] via 44.0.1.4, 00:02:33

O 44.0.3.4/32 [110/75] via 23.0.0.3, 00:16:08, Ethernet0/0

Verify IPv4 BGP neighborship and its details by following command:

BGP neighbor states:

Idle – TCP connectivity issue
Active – Command configuration issue
Established – TCP connectivity established

R2# show bgp ipv4 unicast neighbor

! (Shows details of IPv4 BGP neighbor)

BGP neighbor is 11.0.1.1, remote AS 65100, external link

BGP version 4, remote router ID 11.0.3.1

BGP state = Established, up for 00:02:12

Last read 00:00:22, last write 00:00:31, hold time is 180, keepalive interval is 60 seconds

Neighbor sessions:

1 active, is not multisession capable (disabled)

Neighbor capabilities:

Route refresh: advertised and received(new)

Four-octets ASN Capability: advertised and received

Address family IPv4 Unicast: advertised and received

Enhanced Refresh Capability: advertised and received

Multisession Capability:

Stateful switchover support enabled: NO for session 1

Message statistics:

InQ depth is 0

OutQ depth is 0

Sent Rcvd

Opens: 1 1

Notifications: 0 0

Updates: 4 2

Keepalives: 2 3

Route Refresh: 0 0

Total: 7 6

Default minimum time between advertisement runs is 30 seconds

For address family: IPv4 Unicast

Session: 11.0.1.1

BGP table version 13, neighbor version 13/0

Output queue size : 0

Index 1, Advertise bit 0

1 update-group member

Inbound soft reconfiguration allowed

Slow-peer detection is disabled

Slow-peer split-update-group dynamic is disabled

Sent Rcvd

Prefix activity: ---- ----

Prefixes Current: 9 3 (Consumes 192 bytes)

Prefixes Total: 9 3

Implicit Withdraw: 0 0

Explicit Withdraw: 0 0

Used as bestpath: n/a 3

Used as multipath: n/a 0

Outbound Inbound

Local Policy Denied Prefixes: -------- -------

Bestpath from this peer: 3 n/a

Total: 3 0

Number of NLRIs in the update sent: max 3, min 0

Last detected as dynamic slow peer: never

Dynamic slow peer recovered: never

Refresh Epoch: 1

Last Sent Refresh Start-of-rib: never

Last Sent Refresh End-of-rib: never

Last Received Refresh Start-of-rib: never

Last Received Refresh End-of-rib: never

Sent Rcvd

Refresh activity: ---- ----

Refresh Start-of-RIB 0 0

Refresh End-of-RIB 0 0

Address tracking is enabled, the RIB does have a route to 11.0.1.1

Connections established 1; dropped 0

Last reset never

External BGP neighbor may be up to 5 hops away.

Transport(tcp) path-mtu-discovery is enabled

Graceful-Restart is disabled

Connection state is ESTAB, I/O status: 1, unread input bytes: 0

Connection is ECN Disabled, Mininum incoming TTL 0, Outgoing TTL 5

Local host: 22.0.1.2, Local port: 25173

Foreign host: 11.0.1.1, Foreign port: 179

Connection tableid (VRF): 0

Maximum output segment queue size: 50

Enqueued packets for retransmit: 0, input: 0 mis-ordered: 0 (0 bytes)

Event Timers (current time is 0x24FEA):

Timer Starts Wakeups Next

Retrans 6 0 0x0

TimeWait 0 0 0x0

AckHold 5 3 0x0

SendWnd 0 0 0x0

KeepAlive 0 0 0x0

GiveUp 0 0 0x0

PmtuAger 1 0 0x970C8

DeadWait 0 0 0x0

Linger 0 0 0x0

ProcessQ 0 0 0x0

iss: 144473942 snduna: 144474237 sndnxt: 144474237

irs: 322061158 rcvnxt: 322061358

sndwnd: 16090 scale: 0 maxrcvwnd: 16384

rcvwnd: 16185 scale: 0 delrcvwnd: 199

SRTT: 551 ms, RTTO: 3075 ms, RTV: 2524 ms, KRTT: 0 ms

minRTT: 8 ms, maxRTT: 1000 ms, ACK hold: 200 ms

Status Flags: active open

Option Flags: nagle, path mtu capable

IP Precedence value : 6

Datagrams (max data segment is 1460 bytes):

Rcvd: 10 (out of order: 0), with data: 5, total data bytes: 199

Sent: 11 (retransmit: 0, fastretransmit: 0, partialack: 0, Second Congestion: 0), with data: 5, total data bytes: 294

Packets received in fast path: 0, fast processed: 0, slow path: 0

fast lock acquisition failures: 0, slow path: 0

TCP Semaphore 0xB3A28D24 FREE

BGP neighbor is 33.0.1.3, remote AS 65000, internal link

BGP version 4, remote router ID 33.0.3.3

BGP state = Established, up for 00:01:38

Last read 00:00:09, last write 00:00:08, hold time is 180, keepalive interval is 60 seconds

Neighbor sessions:

1 active, is not multisession capable (disabled)

Neighbor capabilities:

Route refresh: advertised and received(new)

Four-octets ASN Capability: advertised and received

Address family IPv4 Unicast: advertised and received

Enhanced Refresh Capability: advertised and received

Multisession Capability:

Stateful switchover support enabled: NO for session 1

Message statistics:

InQ depth is 0

OutQ depth is 0

Sent Rcvd

Opens: 1 1

Notifications: 0 0

Updates: 3 3

Keepalives: 3 3

Route Refresh: 0 0

Total: 7 7

Default minimum time between advertisement runs is 0 seconds

For address family: IPv4 Unicast

Session: 33.0.1.3

BGP table version 13, neighbor version 13/0

Output queue size : 0

Index 2, Advertise bit 1

2 update-group member

Inbound soft reconfiguration allowed

Slow-peer detection is disabled

Slow-peer split-update-group dynamic is disabled

Sent Rcvd

Prefix activity: ---- ----

Prefixes Current: 6 6 (Consumes 384 bytes)

Prefixes Total: 6 6

Implicit Withdraw: 0 0

Explicit Withdraw: 0 0

Used as bestpath: n/a 6

Used as multipath: n/a 0

Outbound Inbound

Local Policy Denied Prefixes: -------- -------

Bestpath from this peer: 6 n/a

Total: 6 0

Number of NLRIs in the update sent: max 3, min 0

Last detected as dynamic slow peer: never

Dynamic slow peer recovered: never

Refresh Epoch: 1

Last Sent Refresh Start-of-rib: never

Last Sent Refresh End-of-rib: never

Last Received Refresh Start-of-rib: never

Last Received Refresh End-of-rib: never

Sent Rcvd

Refresh activity: ---- ----

Refresh Start-of-RIB 0 0

Refresh End-of-RIB 0 0

Address tracking is enabled, the RIB does have a route to 33.0.1.3

Connections established 1; dropped 0

Last reset never

Transport(tcp) path-mtu-discovery is enabled

Graceful-Restart is disabled

Connection state is ESTAB, I/O status: 1, unread input bytes: 0

Connection is ECN Disabled, Mininum incoming TTL 0, Outgoing TTL 255

Local host: 22.0.1.2, Local port: 179

Foreign host: 33.0.1.3, Foreign port: 35222

Connection tableid (VRF): 0

Maximum output segment queue size: 50

Enqueued packets for retransmit: 0, input: 0 mis-ordered: 0 (0 bytes)

Event Timers (current time is 0x24FEB):

Timer Starts Wakeups Next

Retrans 4 0 0x0

TimeWait 0 0 0x0

AckHold 4 2 0x0

SendWnd 0 0 0x0

KeepAlive 0 0 0x0

GiveUp 0 0 0x0

PmtuAger 0 0 0x0

DeadWait 0 0 0x0

Linger 0 0 0x0

ProcessQ 0 0 0x0

iss: 622847560 snduna: 622847830 sndnxt: 622847830

irs: 1617337082 rcvnxt: 1617337352

sndwnd: 16115 scale: 0 maxrcvwnd: 16384

rcvwnd: 16115 scale: 0 delrcvwnd: 269

SRTT: 413 ms, RTTO: 3205 ms, RTV: 2792 ms, KRTT: 0 ms

minRTT: 0 ms, maxRTT: 1000 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: 10 (out of order: 0), with data: 5, total data bytes: 269

Sent: 10 (retransmit: 0, fastretransmit: 0, partialack: 0, Second Congestion: 0), with data: 5, total data bytes: 269

Packets received in fast path: 0, fast processed: 0, slow path: 0

fast lock acquisition failures: 0, slow path: 0

TCP Semaphore 0xB3A28C44 FREE

Verify IPv4 BGP routes and its details by following command:

R2#show ip bgp

! (Shows IPv4 BGP table where “>” shows best path.)

BGP table version is 13, local router ID is 22.0.3.2

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,

x best-external, a additional-path, c RIB-compressed,

Origin codes: i - IGP, e - EGP, ? - incomplete

RPKI validation codes: V valid, I invalid, N Not found

Network Next Hop Metric LocPrf Weight Path

*> 11.0.1.0/24 11.0.1.1 0 0 65100 i

*> 11.0.2.0/24 11.0.1.1 0 0 65100 i

*> 11.0.3.0/24 11.0.1.1 0 0 65100 i

*> 22.0.1.0/24 0.0.0.0 0 32768 i

*> 22.0.2.0/24 0.0.0.0 0 32768 i

*> 22.0.3.0/24 0.0.0.0 0 32768 i

*>i 33.0.1.0/24 33.0.1.3 0 100 0 i

*>i 33.0.2.0/24 33.0.1.3 0 100 0 i

*>i 33.0.3.0/24 33.0.1.3 0 100 0 i

*>i 44.0.1.0/24 44.0.1.4 0 100 0 65200 i

*>i 44.0.2.0/24 44.0.1.4 0 100 0 65200 i

*>i 44.0.3.0/24 44.0.1.4 0 100 0 65200 i

BGP Local Preference Attributes

September 14, 2016 by

LAB3: BGP – IPv4

Disclaimer

LAB 3: Diagram

Note: This Lab was developed on Cisco IOS Version15.2(4) M1 ADVENTERPRISEK9-M.

LAB3: Configure BGP Local Preference Attributes

Task 1: Configure BGP Local Preference Attributes for Autonomous

In the configuration mode of router configure BGP Local Preference Attributes by following command:

R2:

router bgp 65000

address-family ipv4

neighbor 11.0.1.1 route-map xyz in

exit

route-map xyz permit 10

set local-preference 5000

exit

(A policy is call on Router R2 that to reach 100 network via 11.0.1.1 through AS 65000 preference is set 5000.)

R1:

router bgp 65100

address-family ipv4

neighbor 22.0.1.2 route-map xyz out

exit

route-map xyz permit 10

set local-preference 10000

exit

(A policy is call on Router R1 that to reach 100 network via 22.0.1.2 through AS 65100 preference is set 10000.)

Verify IPv4 BGP routes by following command:

R2#show ip bgp

BGP table version is 32, local router ID is 22.0.3.2

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,

x best-external, a additional-path, c RIB-compressed,

Origin codes: i - IGP, e - EGP, ? - incomplete

RPKI validation codes: V valid, I invalid, N Not found

Network Next Hop Metric LocPrf Weight Path

*> 11.0.1.0/24 11.0.1.1 0 5000 0 65100 i

*> 11.0.2.0/24 11.0.1.1 0 5000 0 65100 i

*> 11.0.3.0/24 11.0.1.1 0 5000 0 65100 i

*> 22.0.1.0/24 0.0.0.0 0 32768 i

*> 22.0.2.0/24 0.0.0.0 0 32768 i

*> 22.0.3.0/24 0.0.0.0 0 32768 i

*>i 33.0.1.0/24 33.0.1.3 0 100 0 i

*>i 33.0.2.0/24 33.0.1.3 0 100 0 i

*>i 33.0.3.0/24 33.0.1.3 0 100 0 i

*>i 44.0.1.0/24 44.0.1.4 0 100 0 65200 i

*>i 44.0.2.0/24 44.0.1.4 0 100 0 65200 i

*>i 44.0.3.0/24 44.0.1.4 0 100 0 65200 i

*> 100.0.0.0/24 11.0.1.1 0 5000 0 65100 i

(Local Preference is by default 100 which is seen only on IBGP neighbor

Local Preference is Local to an Autonomous. It is non-transitive parameter and is stripped of when routes are moving from one AS to another AS.

R2 - Router R2 now selects 11.0.1.1 as best path because it can reach 100 network through As 65200 with Local Preference 5000, where as to reach 100 network via 44.0.1.4 through AS 65200 with Local Preference 100

Hence path is manipulated with help of Local Preference.

We as an Administrator changed the decision of Router R2 to reach 100.0.0.0 network via 44.0.1.4 to path via 11.0.1.1 as best path. Therefore it shows only one path in its BGP Table and is ironically known as Sukhiram.)

R3# show ip bgp

BGP table version is 25, local router ID is 33.0.3.3

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,

x best-external, a additional-path, c RIB-compressed,

Origin codes: i - IGP, e - EGP, ? - incomplete

RPKI validation codes: V valid, I invalid, N Not found

Network Next Hop Metric LocPrf Weight Path

*>i 11.0.1.0/24 11.0.1.1 0 5000 0 65100 i

*>i 11.0.2.0/24 11.0.1.1 0 5000 0 65100 i

*>i 11.0.3.0/24 11.0.1.1 0 5000 0 65100 i

*>i 22.0.1.0/24 22.0.1.2 0 100 0 i

*>i 22.0.2.0/24 22.0.1.2 0 100 0 i

*>i 22.0.3.0/24 22.0.1.2 0 100 0 i

*> 33.0.1.0/24 0.0.0.0 0 32768 i

*> 33.0.2.0/24 0.0.0.0 0 32768 i

*> 33.0.3.0/24 0.0.0.0 0 32768 i

*> 44.0.1.0/24 44.0.1.4 0 0 65200 i

*> 44.0.2.0/24 44.0.1.4 0 0 65200 i

*> 44.0.3.0/24 44.0.1.4 0 0 65200 i

*>i 100.0.0.0/24 11.0.1.1 0 5000 0 65100 i

* 44.0.1.4 0 0 65200 i

(R3-As Local Preference is Local to an Autonomous and R3 belongs to same Autonomous, therefore Router R3 will also select best path as 11.0.1.1 but will show both the path in its BGP table and is ironically known as Dukhiram )

BGP MED Attributes

September 14, 2016 by