Lab 10-1: Route Reflection
A route reflector setup consists of at least one route reflector and one or several route reflector clients that can also be assigned to a logical cluster via a 4-octet cluster ID. When only one route reflector exists, the implicit cluster ID is the loopback address of the router. The basic idea of the designers was that no changes are necessary on the client.
A connection to a single route reflector does suffice to receive and advertise prefixes. For the purpose of redundancy, it is common practice to connect route reflector clients to at least two redundant route reflectors. In addition, large architectures introduce clustering to create multiple logical groups (BGP CLUSTER-LIST attribute).
The cluster ID has to be consistent throughout a cluster. Of course, all route reflectors require full IBGP connectivity among themselves. Figure 10-6 (part a) demonstrates a single-cluster architecture featuring three fully meshed IBGP route reflectors. In this example, two route reflector clients are connected to multiple route reflectors for redundancy. Figure 10-6 (part b) presents a similar topology featuring multiple clusters.
Figure 10-6. Route Reflector Approaches
We start with Example 10-5 featuring a conservative full IBGP mesh among the three UNIX servers running Zebra bgpd and scar running Cisco IOS architecture (which was the topology from Chapter 9, "Dynamic Routing Protocols?Interior Gateway Protocols"). The maximum-paths 6 statement in the scar configuration (highlighted) allows for up to six qualified BGP multipath candidate routes to the same destination to be placed in the routing table for load sharing.
Example 10-5. Zebra IBGP Configurations
ganymed-bgpd# show running-config Current configuration: ! hostname ganymed-bgpd password 8 bJFoEOB0obLL6 enable password 8 bJFoEOB0obLL6 log file /var/log/bgpd.log service advanced-vty service password-encryption ! router bgp 65000 bgp router-id 192.168.44.1 bgp cluster-id 1.1.1.1 redistribute connected neighbor 192.168.1.1 remote-as 65000 neighbor 192.168.1.1 update-source lo1 neighbor 192.168.1.1 soft-reconfiguration inbound neighbor 192.168.2.7 remote-as 65000 neighbor 192.168.2.7 update-source lo1 neighbor 192.168.2.7 soft-reconfiguration inbound neighbor 192.168.201.2 remote-as 65000 neighbor 192.168.201.2 update-source lo1 neighbor 192.168.201.2 soft-reconfiguration inbound ! access-list 1 remark vty-protection access-list 1 permit 127.0.0.1 access-list 1 permit 192.168.1.0 0.0.0.255 ! line vty access-class 1 exec-timeout 15 0 ! end castor-bgpd# show running-config Current configuration: ! hostname castor-bgpd password 8 4DwwIFdKLWvU. enable password 8 dV8x4MhxDAuaw log file /var/log/bgpd.log service advanced-vty service password-encryption ! router bgp 65000 bgp router-id 192.168.2.7 bgp cluster-id 1.1.1.1 redistribute connected neighbor 192.168.1.1 remote-as 65000 neighbor 192.168.1.1 soft-reconfiguration inbound neighbor 192.168.44.1 remote-as 65000 neighbor 192.168.44.1 soft-reconfiguration inbound neighbor 192.168.201.2 remote-as 65000 neighbor 192.168.201.2 soft-reconfiguration inbound ! access-list 1 remark vty-protection access-list 1 permit 127.0.0.1 access-list 1 permit 192.168.1.0 0.0.0.255 ! line vty access-class 1 exec-timeout 15 0 ! end callisto-bgpd# show running-config Current configuration: ! hostname callisto-bgpd password 8 m6eyKycFMHniQ enable password 8 bjYlnA9YLBWyM log file /var/log/bgpd.log service advanced-vty service password-encryption ! router bgp 65000 bgp router-id 192.168.1.1 bgp cluster-id 1.1.1.1 redistribute connected neighbor 192.168.2.7 remote-as 65000 neighbor 192.168.2.7 soft-reconfiguration inbound neighbor 192.168.44.1 remote-as 65000 neighbor 192.168.44.1 soft-reconfiguration inbound neighbor 192.168.201.2 remote-as 65000 neighbor 192.168.201.2 soft-reconfiguration inbound ! access-list 1 remark vty-protection access-list 1 permit 127.0.0.1 access-list 1 permit 192.168.1.0 0.0.0.255 ! line vty access-class 1 exec-timeout 0 0 ! end scar# show running-config ... ! router bgp 65000 bgp router-id 192.168.201.2 bgp cluster-id 1.1.1.1 bgp log-neighbor-changes redistribute connected neighbor 192.168.7.7 remote-as 65000 neighbor 192.168.7.7 update-source Loopback0 neighbor 192.168.7.7 soft-reconfiguration inbound neighbor 192.168.14.1 remote-as 65000 neighbor 192.168.14.1 update-source Loopback0 neighbor 192.168.14.1 soft-reconfiguration inbound neighbor 192.168.44.1 remote-as 65000 neighbor 192.168.44.1 update-source Loopback0 neighbor 192.168.44.1 soft-reconfiguration inbound maximum-paths 6 ! ...
Examples 10-6 and 10-7 demonstrate BGP-related Zebra show commands and Zebra and Cisco IOS architecture debug choices to gain more insight into the "under-the-hood" operation of BGP. In particular, Example 10-6 highlights a BGP example prefix of incomplete origin (highlighted text) due to the redistribution of connected routes. The lab culminates in detailed packet traces in Example 10-8, where we view OPEN and UPDATE messages. Similar analyzer traces regarding KEEPALIVE and NOTIFICATION messages are left as an exercise.
Example 10-6. Zebra BGP Example Output on Ganymed
ganymed-bgpd# show ip bgp BGP table version is 0, local router ID is 192.168.44.1 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal Origin codes: i - IGP, e - EGP, ? - incomplete Network Next Hop Metric LocPrf Weight Path * i192.168.1.0 192.168.1.1 0 100 0 ? *> 0.0.0.0 0 32768 ? * i192.168.2.0 192.168.2.7 0 100 0 ? *> 0.0.0.0 0 32768 ? * i192.168.7.0 192.168.201.2 0 100 0 ? *>i 192.168.2.7 0 100 0 ? *>i192.168.13.0 192.168.201.2 0 100 0 ? * i192.168.14.0 192.168.201.2 0 100 0 ? *>i 192.168.1.1 0 100 0 ? *>i192.168.17.0 192.168.201.2 0 100 0 ? *> 192.168.44.0 0.0.0.0 0 32768 ? * i192.168.45.0 192.168.1.1 0 100 0 ? *> 0.0.0.0 0 32768 ? * i192.168.80.0 192.168.2.7 0 100 0 ? *> 0.0.0.0 0 32768 ? *>i192.168.99.0/30 192.168.1.1 0 100 0 ? *>i192.168.99.2/32 192.168.2.7 0 100 0 ? *>i192.168.201.0 192.168.201.2 0 100 0 ? *> 211.11.117.0 0.0.0.0 0 32768 ? Total number of prefixes 13 ganymed-bgpd# show ip bgp 192.168.80.0 BGP routing table entry for 192.168.80.0/24 Paths: (2 available, best #2, table Default-IP-Routing-Table) Advertised to non peer-group peers: 192.168.1.1 192.168.2.7 192.168.201.2 Local 192.168.2.7 from 192.168.2.7 (192.168.2.7) Origin incomplete, metric 0, localpref 100, valid, internal Last update: Mon Apr 21 11:05:30 2003 Local 0.0.0.0 from 0.0.0.0 (192.168.44.1) Origin incomplete, metric 0, localpref 100, weight 32768, valid, sourced, best Last update: Mon Apr 21 10:12:32 2003 ganymed-bgpd# show ip bgp summary BGP router identifier 192.168.44.1, local AS number 65000 1 BGP AS-PATH entries 0 BGP community entries Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 192.168.1.1 4 65000 395 417 0 0 0 05:20:58 4 192.168.2.7 4 65000 400 417 0 0 0 05:21:05 4 192.168.201.2 4 65000 229 233 0 0 0 00:41:24 5 Total number of neighbors 3 ganymed-bgpd# show ip bgp neighbors BGP neighbor is 192.168.1.1, remote AS 65000, local AS 65000, internal link BGP version 4, remote router ID 192.168.1.1 BGP state = Established, up for 05:21:08 Last read 00:00:08, hold time is 180, keepalive interval is 60 seconds Neighbor capabilities: Route refresh: advertised and received (old and new) Address family IPv4 Unicast: advertised and received Received 394 messages, 2 notifications, 0 in queue Sent 413 messages, 5 notifications, 0 in queue Route refresh request: received 1, sent 1 Minimum time between advertisement runs is 5 seconds Update source is lo1 For address family: IPv4 Unicast Inbound soft reconfiguration allowed Community attribute sent to this neighbor (both) 4 accepted prefixes Connections established 10; dropped 9 Local host: 192.168.44.1, Local port: 34695 Foreign host: 192.168.1.1, Foreign port: 179 Nexthop: 192.168.44.1 Nexthop global: ::1 Nexthop local: fe80::1 BGP connection: non shared network Read thread: on Write thread: off BGP neighbor is 192.168.2.7, remote AS 65000, local AS 65000, internal link BGP version 4, remote router ID 192.168.2.7 BGP state = Established, up for 05:21:15 Last read 00:00:15, hold time is 180, keepalive interval is 60 seconds Neighbor capabilities: Route refresh: advertised and received (old and new) Address family IPv4 Unicast: advertised and received Received 396 messages, 4 notifications, 0 in queue Sent 414 messages, 3 notifications, 0 in queue Route refresh request: received 1, sent 1 Minimum time between advertisement runs is 5 seconds Update source is lo1 For address family: IPv4 Unicast Inbound soft reconfiguration allowed Community attribute sent to this neighbor (both) 4 accepted prefixes Connections established 10; dropped 9 Local host: 192.168.44.1, Local port: 179 Foreign host: 192.168.2.7, Foreign port: 1062 Nexthop: 192.168.44.1 Nexthop global: ::1 Nexthop local: fe80::1 BGP connection: non shared network Read thread: on Write thread: off BGP neighbor is 192.168.201.2, remote AS 65000, local AS 65000, internal link BGP version 4, remote router ID 192.168.201.2 BGP state = Established, up for 00:41:34 Last read 00:00:33, hold time is 180, keepalive interval is 60 seconds Neighbor capabilities: Route refresh: advertised and received (old and new) Address family IPv4 Unicast: advertised and received Received 229 messages, 0 notifications, 0 in queue Sent 232 messages, 1 notifications, 0 in queue Route refresh request: received 0, sent 0 Minimum time between advertisement runs is 5 seconds Update source is lo1 For address family: IPv4 Unicast Inbound soft reconfiguration allowed Community attribute sent to this neighbor (both) 5 accepted prefixes Connections established 5; dropped 4 Local host: 192.168.44.1, Local port: 7928 Foreign host: 192.168.201.2, Foreign port: 179 Nexthop: 192.168.44.1 Nexthop global: ::1 Nexthop local: fe80::1 BGP connection: non shared network Read thread: on Write thread: off ganymed-bgpd# show ip bgp neighbors 192.168.1.1 advertised-routes BGP table version is 0, local router ID is 192.168.44.1 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal Origin codes: i - IGP, e - EGP, ? - incomplete Network Next Hop Metric LocPrf Weight Path *> 192.168.1.0 192.168.44.1 0 100 32768 ? *> 192.168.2.0 192.168.44.1 0 100 32768 ? *> 192.168.44.0 192.168.44.1 0 100 32768 ? *> 192.168.45.0 192.168.44.1 0 100 32768 ? *> 192.168.80.0 192.168.44.1 0 100 32768 ? *> 211.11.117.0 192.168.44.1 0 100 32768 ? Total number of prefixes 6
Example 10-7. Cisco IOS Architecture and Zebra BGP Debug Choices
scar# debug ip bgp ? A.B.C.D BGP neighbor address dampening BGP dampening events BGP events in BGP Inbound information keepalives BGP keepalives out BGP Outbound information updates BGP updates vpnv4 VPNv4 NLRI information scar# debug ip bgp BGP debugging is on scar# clear ip bgp 192.168.14.1 00:30:33: BGP: 192.168.14.1 went from Established to Idle *Mar 1 00:30:36: %BGP-5-ADJCHANGE: neighbor 192.168.14.1 Down User reset 00:30:33: BGP: 192.168.14.1 closing 00:30:33: BGP: 192.168.14.1 went from Idle to Active 00:30:33: BGP: 192.168.14.1 open active, delay 7016ms 00:30:40: BGP: 192.168.14.1 open active, local address 192.168.201.2 00:30:40: BGP: 192.168.14.1 went from Active to OpenSent 00:30:40: BGP: 192.168.14.1 sending OPEN, version 4, my as: 65000 00:30:40: BGP: 192.168.14.1 send message type 1, length (incl. header) 45 00:30:40: BGP: 192.168.14.1 rcv message type 1, length (excl. header) 26 00:30:40: BGP: 192.168.14.1 rcv OPEN, version 4 00:30:40: BGP: 192.168.14.1 rcv OPEN w/ OPTION parameter len: 16 00:30:40: BGP: 192.168.14.1 rcvd OPEN w/ optional parameter type 2 (Capability) len 6 00:30:40: BGP: 192.168.14.1 OPEN has CAPABILITY code: 1, length 4 00:30:40: BGP: 192.168.14.1 OPEN has MP_EXT CAP for afi/safi: 1/1 00:30:40: BGP: 192.168.14.1 rcvd OPEN w/ optional parameter type 2 (Capability) len 2 00:30:40: BGP: 192.168.14.1 OPEN has CAPABILITY code: 128, length 0 00:30:40: BGP: 192.168.14.1 OPEN has ROUTE-REFRESH capability(old) for all address-families 00:30:40: BGP: 192.168.14.1 rcvd OPEN w/ optional parameter type 2 (Capability) len 2 00:30:40: BGP: 192.168.14.1 OPEN has CAPABILITY code: 2, length 0 00:30:40: BGP: 192.168.14.1 OPEN has ROUTE-REFRESH capability(new) for all address-families 00:30:40: BGP: 192.168.14.1 went from OpenSent to OpenConfirm 00:30:40: BGP: 192.168.14.1 send message type 4, length (incl. header) 19 00:30:40: BGP: 192.168.14.1 rcv message type 4, length (excl. header) 0 00:30:40: BGP: 192.168.14.1 went from OpenConfirm to Established *Mar 1 00:30:43: %BGP-5-ADJCHANGE: neighbor 192.168.14.1 Up 00:30:41: BGP: 192.168.14.1 send message type 4, length (incl. header) 19 00:30:41: BGP: 192.168.14.1 send message type 4, length (incl. header) 19 00:30:41: BGP: 192.168.14.1 rcv message type 4, length (excl. header) 0 00:30:54: BGP: 192.168.7.7 send message type 4, length (incl. header) 19 00:30:54: BGP: 192.168.7.7 rcv message type 4, length (excl. header) 0 00:30:57: BGP: 192.168.44.1 send message type 4, length (incl. header) 19 00:30:57: BGP: 192.168.44.1 rcv message type 4, length (excl. header) 0 00:31:22: BGP: Applying map to find origin for 192.168.13.0/29 00:31:22: BGP: Applying map to find origin for 192.168.14.0/24 00:31:22: BGP: Applying map to find origin for 192.168.201.0/32 00:31:22: BGP: Applying map to find origin for 192.168.7.0/24 00:31:22: BGP: Applying map to find origin for 192.168.17.0/29 00:31:40: BGP: 192.168.14.1 send message type 4, length (incl. header) 19 00:31:40: BGP: 192.168.14.1 rcv message type 4, length (excl. header) 0 00:31:54: BGP: 192.168.7.7 send message type 4, length (incl. header) 19 00:31:54: BGP: 192.168.7.7 rcv message type 4, length (excl. header) 0 00:31:57: BGP: 192.168.44.1 send message type 4, length (incl. header) 19 00:31:57: BGP: 192.168.44.1 rcv message type 4, length (excl. header) 0 scar# show ip bgp summary BGP router identifier 192.168.201.2, local AS number 65000 BGP table version is 11, main routing table version 11 13 network entries and 19 paths using 1945 bytes of memory 2 BGP path attribute entries using 120 bytes of memory 0 BGP route-map cache entries using 0 bytes of memory 0 BGP filter-list cache entries using 0 bytes of memory BGP activity 26/13 prefixes, 38/19 paths, scan interval 60 secs Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 192.168.7.7 4 65000 21 23 11 0 0 00:00:59 4 192.168.14.1 4 65000 21 24 11 0 0 00:00:39 4 192.168.44.1 4 65000 22 24 11 0 0 00:01:02 6 # # The effect on callisto (the peer router): # callisto-bgpd# debug bgp ? events BGP events filters BGP filters fsm BGP Finite State Machine keepalives BGP keepalives updates BGP updates callisto-bgpd# debug bgp BGP debugging is on callisto-bgpd# BGP: 192.168.201.2 went from Established to Idle BGP: 192.168.201.2 went from Idle to Connect BGP: 192.168.201.2 went from Connect to Active BGP: Performing BGP general scanning BGP: 192.168.2.7 send message type 4, length (incl. header) 19 BGP: 192.168.2.7 rcv message type 4, length (excl. header) 0 BGP: 192.168.201.2 went from Active to OpenSent BGP: 192.168.201.2 rcv message type 1, length (excl. header) 26 BGP: 192.168.201.2 rcv OPEN, version 4, remote-as 65000, holdtime 180, id 192.168.201.2 BGP: 192.168.201.2 sending OPEN, version 4, my as 65000, holdtime 180, id 192.168.1.1 BGP: 192.168.201.2 send message type 1, length (incl. header) 45 BGP: 192.168.201.2 rcv OPEN w/ OPTION parameter len: 16 BGP: 192.168.201.2 rcvd OPEN w/ optional parameter type 2 (Capability) len 6 BGP: 192.168.201.2 OPEN has CAPABILITY code: 1, length 4 BGP: 192.168.201.2 OPEN has MP_EXT CAP for afi/safi: 1/1 BGP: 192.168.201.2 rcvd OPEN w/ optional parameter type 2 (Capability) len 2 BGP: 192.168.201.2 OPEN has CAPABILITY code: 128, length 0 BGP: 192.168.201.2 OPEN has ROUTE-REFRESH capability(old) for all address-families BGP: 192.168.201.2 rcvd OPEN w/ optional parameter type 2 (Capability) len 2 BGP: 192.168.201.2 OPEN has CAPABILITY code: 2, length 0 BGP: 192.168.201.2 OPEN has ROUTE-REFRESH capability(new) for all address-families BGP: 192.168.201.2 went from OpenSent to OpenConfirm BGP: 192.168.201.2 send message type 4, length (incl. header) 19 BGP: 192.168.201.2 rcv message type 4, length (excl. header) 0 BGP: 192.168.201.2 went from OpenConfirm to Established BGP: 192.168.201.2 send message type 4, length (incl. header) 19 BGP: 192.168.201.2 rcv message type 4, length (excl. header) 0 BGP: 192.168.201.2 rcv message type 4, length (excl. header) 0 BGP: 192.168.44.1 send message type 4, length (incl. header) 19 BGP: 192.168.44.1 rcv message type 4, length (excl. header) 0 BGP: Performing BGP general scanning BGP: 192.168.2.7 send message type 4, length (incl. header) 19 BGP: 192.168.2.7 rcv message type 4, length (excl. header) 0 BGP: 192.168.201.2 send message type 4, length (incl. header) 19 BGP: 192.168.201.2 rcv message type 4, length (excl. header) 0 BGP: 192.168.44.1 send message type 4, length (incl. header) 19 BGP: 192.168.44.1 rcv message type 4, length (excl. header) 0 callisto-bgpd# show ip bgp summary BGP router identifier 192.168.1.1, local AS number 65000 1 BGP AS-PATH entries 0 BGP community entries Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 192.168.2.7 4 65000 347 356 0 0 0 04:44:50 4 192.168.44.1 4 65000 350 359 0 0 0 04:44:42 6 192.168.201.2 4 65000 188 197 0 0 0 00:04:45 5 Total number of neighbors 3
Example 10-8. BGP Peer Negotiation Sniffer Traces on Callisto
# # The big picture: # [root@callisto:#] tethereal ?i eth0 0.248208 192.168.201.2 -> 192.168.14.1 TCP 11008 > bgp [FIN, PSH, ACK] Seq=2941710864Ack=2857752019 Win=16176 Len=0 0.266164 192.168.201.2 -> 192.168.14.1 TCP 11008 > bgp [ACK] Seq=2941710865
Obviously, configuring full-meshed IBGP networks does not scale. To remedy this shortcoming, ganymed was configured as a route reflector for scar, castor, and callisto. All routers inhabit the same cluster with the BGP cluster ID 1.1.1.1. Therefore, the configuration of a cluster ID is redundant, although it is a good idea in large architectures. Example 10-9 demonstrates this setup in combination with peer groups, including statements valid for all peer-group members.
Example 10-9. IBGP Lab Improvement (Cluster ID, Ganymed as Route Reflector Server, Peer Group)
ganymed-bgpd# show running-config Current configuration: ! hostname ganymed-bgpd password 8 bJFoEOB0obLL6 enable password 8 bJFoEOB0obLL6 log file /var/log/bgpd.log service advanced-vty service password-encryption ! router bgp 65000 bgp router-id 192.168.44.1 bgp cluster-id 1.1.1.1 redistribute connected neighbor INTERNAL peer-group neighbor INTERNAL remote-as 65000 neighbor INTERNAL update-source lo1 neighbor INTERNAL route-reflector-client neighbor INTERNAL soft-reconfiguration inbound neighbor 192.168.1.1 peer-group INTERNAL neighbor 192.168.2.7 peer-group INTERNAL neighbor 192.168.201.2 peer-group INTERNAL ! access-list 1 remark vty-protection access-list 1 permit 127.0.0.1 access-list 1 permit 192.168.1.0 0.0.0.255 ! line vty access-class 1 exec-timeout 15 0 ! end scar# show running-config ... ! router bgp 65000 bgp router-id 192.168.201.2 bgp cluster-id 1.1.1.1 bgp log-neighbor-changes redistribute connected neighbor 192.168.44.1 remote-as 65000 neighbor 192.168.44.1 update-source Loopback0 neighbor 192.168.44.1 soft-reconfiguration inbound maximum-paths 6 ! ... scar# show ip bgp neighbors BGP neighbor is 192.168.44.1, remote AS 65000, internal link BGP version 4, remote router ID 192.168.44.1 BGP state = Established, up for 00:02:42 Last read 00:00:42, hold time is 180, keepalive interval is 60 seconds Neighbor capabilities: Route refresh: advertised and received(new) Address family IPv4 Unicast: advertised and received Received 150 messages, 5 notifications, 0 in queue Sent 143 messages, 0 notifications, 0 in queue Route refresh request: received 1, sent 0 Default minimum time between advertisement runs is 5 seconds For address family: IPv4 Unicast BGP table version 6, neighbor version 6 Index 3, Offset 0, Mask 0x8 Inbound soft reconfiguration allowed 6 accepted prefixes consume 216 bytes Prefix advertised 55, suppressed 0, withdrawn 0 Number of NLRIs in the update sent: max 5, min 0 Connections established 10; dropped 9 Last reset 00:02:57, due to BGP Notification received, cease Connection state is ESTAB, I/O status: 1, unread input bytes: 0 Local host: 192.168.201.2, Local port: 179 Foreign host: 192.168.44.1, Foreign port: 11513 Enqueued packets for retransmit: 0, input: 0 mis-ordered: 0 (0 bytes) Event Timers (current time is 0x5C4870): Timer Starts Wakeups Next Retrans 8 0 0x0 TimeWait 0 0 0x0 AckHold 8 2 0x0 SendWnd 0 0 0x0 KeepAlive 0 0 0x0 GiveUp 0 0 0x0 PmtuAger 0 0 0x0 DeadWait 0 0 0x0 iss: 465643069 snduna: 465643281 sndnxt: 465643281 sndwnd: 16616 irs: 3432198257 rcvnxt: 3432198602 rcvwnd: 16040 delrcvwnd: 344 SRTT: 197 ms, RTTO: 984 ms, RTV: 787 ms, KRTT: 0 ms minRTT: 4 ms, maxRTT: 300 ms, ACK hold: 200 ms Flags: passive open, nagle, gen tcbs Datagrams (max data segment is 536 bytes): Rcvd: 14 (out of order: 0), with data: 8, total data bytes: 344 Sent: 10 (retransmit: 0), with data: 7, total data bytes: 211 scar# show ip bgp summary BGP router identifier 192.168.201.2, local AS number 65000 BGP table version is 6, main routing table version 6 11 network entries and 11 paths using 1463 bytes of memory 2 BGP path attribute entries using 120 bytes of memory 0 BGP route-map cache entries using 0 bytes of memory 0 BGP filter-list cache entries using 0 bytes of memory BGP activity 65/76 prefixes, 137/126 paths, scan interval 60 secs Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 192.168.44.1 4 65000 151 144 6 0 0 00:03:31 6 scar# show ip bgp BGP table version is 6, local router ID is 192.168.201.2 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal Origin codes: i - IGP, e - EGP, ? - incomplete Network Next Hop Metric LocPrf Weight Path * i192.168.1.0 192.168.44.1 0 100 0 ? * i192.168.2.0 192.168.44.1 0 100 0 ? *> 192.168.7.0 0.0.0.0 0 32768 ? *> 192.168.13.0 0.0.0.0 0 32768 ? *> 192.168.14.0 0.0.0.0 0 32768 ? *> 192.168.17.0 0.0.0.0 0 32768 ? * i192.168.44.0 192.168.44.1 0 100 0 ? * i192.168.45.0 192.168.44.1 0 100 0 ? * i192.168.80.0 192.168.44.1 0 100 0 ? *> 192.168.201.0 0.0.0.0 0 32768 ? * i211.11.117.0 192.168.44.1 0 100 0 ?
Exercise 10-1: BGP and IGP Interaction
For demonstration purposes, stop the underlying OSPF Zebra daemon ospfd. This will result in some IBGP sessions remaining in ACTIVE state because of the loss of IGP connectivity to some interfaces (especially the loopbacks).
Exercise 10-2: BGP Synchronization
Turn off IGP synchronization and experiment with the behavior within a transit AS. Develop a good understanding of potential AS traversal problems.
