While implementing TTL security, you issue the PE(config-router-af)#neighbor 2.2.2.2 ttl-security hops 2 command.
After you issue this command, which BGP packets does the PE accept?
While implementing TTL security, you issue the PE(config-router-af)#neighbor 2.2.2.2 ttl-security hops 2 command.
After you issue this command, which BGP packets does the PE accept?
When configuring TTL security with the command 'neighbor 2.2.2.2 ttl-security hops 2', the router expects to receive BGP packets from the neighbor with a TTL value of at least 253. This is calculated as 255 (the maximum TTL value) minus the number of hops set (2). Therefore, the correct answer is that the PE accepts packets from 2.2.2.2 with a TTL of 253 or more.
It's D -------------------------------------------------- neighbor 10.1.1.1 ttl-security hops 2 The example configuration sets the expected incoming TTL value to at least 253, which is 255 minus the TTL value of 2, and this is the minimum TTL value expected from the BGP peer. The local router will accept the peering session from the 10.1.1.1 neighbor only if it is 1 or 2 hops away. -------------------------------------------------------------- https://www.cisco.com/c/en/us/td/docs/ios/12_2sx/feature/guide/fsxebtsh.html#wp1059215
Example: Router(config-router)# neighbor 10.1.1.1 ttl-security hops 2 The example configuration sets the expected incoming TTL value to at least 253, which is 255 minus the TTL value of 2, and this is the minimum TTL value expected from the BGP peer. The local router will accept the peering session from the 10.1.1.1 neighbor only if it is 1 or 2 hops away. https://www.cisco.com/c/en/us/td/docs/ios/12_2sx/feature/guide/fsxebtsh.html
According to Cisco, the expected ping response from the neighbor should be 253 or greater because 255-253=2 or 255-254=1 which means that the neighbor is 2 or 1 hops away.
the expected incoming TTL value to at least 253 Reference: https://www.cisco.com/c/en/us/td/docs/ios/12_2sx/feature/guide/fsxebtsh.html
It's B. from 2.2.2.2, with a TTL of less than 2
That's not right, it's 253 or more. 255-2 = 253
neighbor 10.1.1.1 ttl-security hops 2 The local router will accept the peering session from the 10.1.1.1 neighbor only if it is 1 or 2 hops away. https://www.cisco.com/c/en/us/td/docs/ios/12_2sx/feature/guide/fsxebtsh.html#wp1059215