Missing Diagram Portion of exhibit


https://www.scribd.com/document/65704362...-2023-v1-2

Exhibit is incorrect 

Table shows device id's as ASBR 2,3,4

Diagram shows ASBR 1,2,3

Who is to say the misconfiguration isn't on e0/1 of Cape Town?

CapeTown#sh ip route | inc 192.168.1.0
D    192.168.1.0/24 [90/665600] via 192.168.12.1, 00:00:05, Ethernet0/0
CapeTown#
CapeTown#

CapeTown#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
CapeTown(config)#int e 0/1
CapeTown(config-if)#band 10000
CapeTown(config-if)#end
CapeTown#
CapeTown#
CapeTown#
*Feb 18 04:29:55.827: %SYS-5-CONFIG_I: Configured from console by console
CapeTown#
CapeTown#
CapeTown#sh ip route | inc 192.168.1.0
D    192.168.1.0/24 [90/435200] via 192.168.13.2, 00:00:05, Ethernet0/1
CapeTown#

The Router-ID is the tie breaker in the AS Path Selection. Path 6 wins because of its lowest Router-ID. Path 5 (RID 10.77.255.57) comes in second.

1. Weight - not a factor... no option mentions weight
2. Local Preference - Same value (100) on all paths
3. Origin Code - Same value (learned) on all paths.
4. Path Length - Same on all devices (1) an AS_Set counts as one
5. Origin ID - Same on all Devices (IGP)
6. MED - Same on all devices (0)
7. Prefer eBGP over iBGP - all paths are internal There is no distinction between Conferderation External and Confederation Internal.
8. IGP Metric - Same value (20645) on all paths.
9. Multipath - not used
10. if both paths are external, choose oldest path. not used
11. Lowest Router-ID Path 6 wins,  Path 5 is second.

Changing the Local_Pref could have the desired effect but the wording is incorrect.  Lowering the LOCAL_PREF does not select AS THE BEST PATH, you would need to raise the LOCAL_PREF for this to happen.  

Prepending the AS_PATH for the current best path would move path 6 from first to worst.  Path 5 would become the new best path. 

https://www.cisco.com/c/en/us/support/do...753-25.pdf

Only Allow Networks that Originate from AS 4 to Enter Router 1


Placing 'ip as-path access-list 1 permit ^111$ on ISP-1 only allows ISP-1 to receive routers from AS111.  


See example from 
https://www.cisco.com/c/en/us/support/do...1227473857


If you would like for Router 1 to receive only the routes originated from AS 4 (and no Internet routes), you can apply an inbound access list on Router 1:

Quote:ip as-path access-list 1 permit ^4$
router bgp 1
neighbor 10.4.4.4 remote-as 4
neighbor 10.4.4.4 route-map foo in
route-map foo permit 10
match as-path 1

OSPFv2 supports IPv4, while OSPFv3 supports IPv6.

https://content.cisco.com/chapter.sjs?ur...0.html.xml

The server has a known IP address of 2::2/64

To be able to enable OSPFv3 on an interface, the interface must be enabled for IPv6. This occurs when the interface is configured with a global unicast IPv6 address.

https://www.ciscopress.com/articles/arti...4&seqNum=4


Since there is no mention of IPv6 to IPv4 NAT, we must select the option to use IPv6 to connect to the server at Center (2::2/64).  This assumes that the command "ipv6 ospf 1 area 2" falls under IPv6 configruation but is still the best answer.

BFD Detects path failures between 2 adjacent routers.  A routing protocol failure could be a result of a misconfiguration. 
https://www.cisco.com/c/en/us/td/docs/io...s_bfd.html


BFD is a detection protocol designed to provide fast forwarding path failure detection times for all media types, encapsulations, topologies, and routing protocols. In addition to fast forwarding path failure detection, BFD provides a consistent failure detection method for network administrators. Because the network administrator can use BFD to detect forwarding path failures at a uniform rate, rather than the variable rates for different routing protocol hello mechanisms, network profiling and planning will be easier, and reconvergence time will be consistent and predictable.

https:// www. examguides. com / CCNP-ENARSI/ ccnp-enarsi-cramnotes-4.htm



bfd interval milliseconds min_rx milliseconds multiplier interval-multiplier
https://www.cisco.com/c/en/us/td/docs/io...#wp1053749

The Bidirectional Forwarding Detection (BFD) protocol is a simple hello mechanism that detects failures in a network. Hello packets are sent at a specified, regular interval. A neighbor failure is detected when the routing device stops receiving a reply after a specified interval.

https://www.juniper.net/documentation/us...20interval.

The redistribute command option to match external includes both E1 and E2 Subnets.  The keyword 'external' is converted to 'External 1 and External 2' in the running config.  


IOU2#sh ip route | inc E1 | E2
      E1 - OSPF external type 1, E2 - OSPF external type 2
O E2    4.4.4.0 [110/20] via 192.168.12.1, 00:12:40, Ethernet1/0
O E1    6.6.6.0 [110/40] via 192.168.12.1, 00:13:01, Ethernet1/0
O E1  192.168.56.0/24 [110/40] via 192.168.12.1, 00:35:06, Ethernet1/0
IOU2#
IOU2#
IOU2#show run | section router eigrp
router eigrp 1
network 2.0.0.0
network 192.168.23.0
IOU2#
IOU2#
IOU2#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
IOU2(config)#router eigrp 1
IOU2(config-router)#redistribute ospf 1 match external  metric 10000 2000 255 1 1500 route-map OSPF-TO-EIGRP
IOU2(config-router)#end
IOU2#
IOU2#
IOU2#sh run | section router eigrp
router eigrp 1
network 2.0.0.0
network 192.168.23.0
redistribute ospf 1 match external 1 external 2 metric 10000 2000 255 1 1500 route-map OSPF-TO-EIGRP
IOU2#

######################################################################

IOU3#sh ip route | inc EX
      D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
D EX    4.4.4.0 [170/793600] via 192.168.23.2, 00:07:02, Ethernet0/0
D EX    6.6.6.0 [170/793600] via 192.168.23.2, 00:07:02, Ethernet0/0
IOU3#

Auto summarization determines which routes are advertised.  R1 and R3 are both advertising 172.16.0.0/16.  

Changing auto summarization on R2 will have no impact.

adding a static route to 172.16.2.0 with a more specific mask will resolve the issue




IOU2# sh 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
      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
      a - application route
      + - replicated route, % - next hop override, p - overrides from PfR

Gateway of last resort is not set

      10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
C        10.1.1.0/24 is directly connected, Ethernet1/0
L        10.1.1.2/32 is directly connected, Ethernet1/0
C        10.1.2.0/24 is directly connected, Ethernet0/0
L        10.1.2.2/32 is directly connected, Ethernet0/0
D    172.16.0.0/16 [90/409600] via 10.1.2.3, 00:00:07, Ethernet0/0
                    [90/409600] via 10.1.1.1, 00:00:07, Ethernet1/0
IOU2#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
IOU2(config)#router eigrp 100
IOU2(config-router)#no auto
IOU2(config-router)#

IOU2(config-router)#do sh 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
      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
      a - application route
      + - replicated route, % - next hop override, p - overrides from PfR

Gateway of last resort is not set

      10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
C        10.1.1.0/24 is directly connected, Ethernet1/0
L        10.1.1.2/32 is directly connected, Ethernet1/0
C        10.1.2.0/24 is directly connected, Ethernet0/0
L        10.1.2.2/32 is directly connected, Ethernet0/0
D    172.16.0.0/16 [90/409600] via 10.1.2.3, 00:00:31, Ethernet0/0
                    [90/409600] via 10.1.1.1, 00:00:31, Ethernet1/0
IOU2(config-router)#exit
IOU2(config)#ip route 172.17.2.0 255.255.255.0 10.1.2.3 254
IOU2(config)#do sh 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
      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
      a - application route
      + - replicated route, % - next hop override, p - overrides from PfR

Gateway of last resort is not set

      10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
C        10.1.1.0/24 is directly connected, Ethernet1/0
L        10.1.1.2/32 is directly connected, Ethernet1/0
C        10.1.2.0/24 is directly connected, Ethernet0/0
L        10.1.2.2/32 is directly connected, Ethernet0/0
D    172.16.0.0/16 [90/409600] via 10.1.2.3, 00:01:23, Ethernet0/0
                    [90/409600] via 10.1.1.1, 00:01:23, Ethernet1/0
      172.17.0.0/24 is subnetted, 1 subnets
S        172.17.2.0 [254/0] via 10.1.2.3
IOU2(config)#
IOU2#
*Feb 15 17:02:03.432: %SYS-5-CONFIG_I: Configured from console by console
IOU2#

Exhibit has unknown characters

EIGRP Summarization should  be configured at R1's neighbor to correct this problem.  Changing the summary-address at R1 would determine what summary addresses R1 advertises.

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