Find AS-Number BGP Neighbor without Ask Administrator

I have topology with 2 router (router A & router B) :

(A) 172.16.0.1 ---- 172.16.0.2 (B)
ASN.65000 ---- ASN.65535

- (A) already config BGP with
router bgp 65000
neighbor 172.16.0.2 remote-as 65535

- (B) want to connect with A via BGP
- (B) not yet get information ASN (A)
- (B) how to find AS-Number (A) without ask administrator ?

1. config AS-Number (B)
router bgp 65535 ---> ASN (B)

2. config neighbor valid IP (A) & whatever AS-Number (A)
neighbor 172.16.0.1 remote-as 1 ---> ASN.1 is whatever AS-Number, just trigger log error

3. config bgp-log
router bgp 65535
bgp log-neighbor-changes ---> to show notification log error

- in router (B) will generate log :
%BGP-3-NOTIFICATION: sent to neighbor 172.16.0.1 2/2 (peer in wrong AS) 2 bytes FDE8

chars FDE8 is hexadecimal AS-Number (A)
convert hexadecimal FDE8 to decimal = 65000

- change your config
neighbor 172.16.0.1 remote-as 65000

- in router (B) will generate log :
%BGP-5-ADJCHANGE: neighbor 172.16.0.1 Up

Now you can find AS-Number BGP neighbor without ask administrator ;)

Manual reroute traffic 'ip ospf cost' better than auto reroute

Router1#sh ip os int b
Interface    PID   Area            IP Address/Mask    Cost  State Nbrs F/C
Vl50         1     0               161.1.79.7/24      300   DR    1/1
Fa0/15       1     0               161.1.78.7/24      100   BDR   1/1
Lo0          1     0               150.1.7.7/24       1     LOOP  0/0

Router2#sh ip os int b
Interface    PID   Area            IP Address/Mask    Cost  State Nbrs F/C
Fa0/16       1     0               161.1.89.8/24      150   DR    1/1
Fa0/15       1     0               161.1.78.8/24      100   DR    1/1
Lo0          1     0               150.1.8.8/24       1     LOOP  0/0

Router3#sh ip os int b
Interface    PID   Area            IP Address/Mask    Cost  State Nbrs F/C
Fa0/16       1     0               161.1.89.9/24      150   BDR   1/1
Vl50         1     0               161.1.79.9/24      300   BDR   1/1
Lo0          1     0               150.1.9.9/24       1     LOOP  0/0

Router3#sh ip ro 150.1.7.7
Routing entry for 150.1.7.7/32
  Known via "ospf 1", distance 110, metric 251, type intra area
  Last update from 161.1.89.8 on FastEthernet0/16, 00:04:39 ago
  Routing Descriptor Blocks:
  * 161.1.89.8, from 150.1.7.7, 00:04:39 ago, via FastEthernet0/16
      Route metric is 251, traffic share count is 1

Router3#traceroute 150.1.7.7
Type escape sequence to abort.
Tracing the route to 150.1.7.7
  1 161.1.89.8 0 msec 4 msec 0 msec
  2 161.1.78.7 4 msec *  0 msec

# SCENARIO I, Change cost with 'ip ospf cost 50'

Router3(config)#do sh ip os int b
Interface    PID   Area            IP Address/Mask    Cost  State Nbrs F/C
Fa0/16       1     0               161.1.89.9/24      150   BDR   1/1
Vl50         1     0               161.1.79.9/24      50    BDR   1/1
Lo0          1     0               150.1.9.9/24       1     LOOP  0/0

Router3(config)#do sh ip ro 150.1.7.7
Routing entry for 150.1.7.7/32
  Known via "ospf 1", distance 110, metric 51, type intra area
  Last update from 161.1.79.7 on Vlan50, 00:00:36 ago
  Routing Descriptor Blocks:
  * 161.1.79.7, from 150.1.7.7, 00:00:36 ago, via Vlan50
      Route metric is 51, traffic share count is 1

Router3(config)#do traceroute 150.1.7.7
Type escape sequence to abort.
Tracing the route to 150.1.7.7
  1 161.1.79.7 4 msec *  0 msec

>> Verify with ping, during I change cost 50

Router3#ping 150.1.7.7 repeat 10000
Success rate is 100 percent (10000/10000), round-trip min/avg/max = 1/1/28 ms

# SCENARIO II, Force shutdown interface FastEternet0/15 in Router1 (Router1-Router2)
traffic from Router3 to Router 1 should be route to interface vlan 50 (Router1-Router3)

Router3(config-if)#do sh ip ro 150.1.7.7
Routing entry for 150.1.7.7/32
  Known via "ospf 1", distance 110, metric 301, type intra area
  Last update from 161.1.79.7 on Vlan50, 00:00:29 ago
  Routing Descriptor Blocks:
  * 161.1.79.7, from 150.1.7.7, 00:00:29 ago, via Vlan50
      Route metric is 301, traffic share count is 1

Router3(config-if)#do traceroute 150.1.7.7
Type escape sequence to abort.
Tracing the route to 150.1.7.7
  1 161.1.79.7 0 msec *  0 msec

>> Verify with ping, during I force shutdown

Router3#ping 150.1.7.7 repeat 10000
Success rate is 99 percent (9995/10000), round-trip min/avg/max = 1/1/216 ms

Vlan VTP Client doesn't updated

Let's back to classic mode :d learning and exploring about Cisco again. In a few months ago I'm on next mode (*red. exploring about new stuff/things).

I ever happen vlan in VTP client doesn't updated, I have 3 switch for example. SW1, SW2, SW3, SW1 mode server, SW2 and SW3 mode client. SW1 and SW2 have trunk, SW1 and SW3 have trunk too. VTP configuration set domain TEST, no password. Vlan in SW2 has beed updated same with SW1 but SW3 doesn't updated, there are some procedure I do :

- re-check trunk configuration, re-config if need
- re-check vtp configuration, re-config if need
- make sure MD5 digest same on SW1 and SW3, if different try to set password first in SW3 'vtp password TEST' and then disable 'no vtp password'. if still different, try to set / disable password in SW1, SW3 and don't forget set / disable password too in all vtp client switch SW2.

SW1(config)#do sh vtp stat
VTP Version : 2
Configuration Revision : 2
Maximum VLANs supported locally : 1005
Number of existing VLANs : 12
VTP Operating Mode : Server
VTP Domain Name : TEST
VTP Pruning Mode : Disabled
VTP V2 Mode : Disabled
VTP Traps Generation : Disabled
MD5 digest : 0xBE 0xE2 0xB5 0xC3 0x82 0x11 0xFA 0x9C

SW3(config)#do sh vtp stat
VTP Version : 2
Configuration Revision : 0
Maximum VLANs supported locally : 1005
Number of existing VLANs : 5
VTP Operating Mode : Client
VTP Domain Name : TEST
VTP Pruning Mode : Disabled
VTP V2 Mode : Disabled
VTP Traps Generation : Disabled
MD5 digest : 0xF6 0xA0 0x56 0x82 0x84 0xD4 0xBF 0xF6

SW3(config)#vtp pass test
Setting device VLAN database password to test
SW3(config)#no vtp pass
Clearing device VLAN database password.

SW3(config)#do sh vtp stat
VTP Version : 2
Configuration Revision : 2
Maximum VLANs supported locally : 1005
Number of existing VLANs : 12
VTP Operating Mode : Client
VTP Domain Name : TEST
VTP Pruning Mode : Disabled
VTP V2 Mode : Disabled
VTP Traps Generation : Disabled
MD5 digest : 0xBE 0xE2 0xB5 0xC3 0x82 0x11 0xFA 0x9C