Refer to the exhibit.
An enterprise network has an upstream connection to two different ISPs that are using eBGP and
a publicly assigned PI network.
ISP1 is used as the primary provider, while ISP2 is used for backup. Due to packet loss on the link
to ISP1, the network engineers changed the default route on R1 to point to ISP2, but they could
not establish any connection until they changed the default route to point back at ISP1.
Which two are possible root causes of the issue? (Choose two.)
A.
“ip verify unicast source reachable-via rx” is configured on the R1 uplinks.
B.
“ip verify unicast source reachable-via any” is configured on the R1 uplinks.
C.
“ip verify unicast source reachable-via rx” is configured on the ISP1 link to R1.
D.
“ip verify unicast source reachable-via any” is configured on the ISP1 link to R1.
E.
“ip verify unicast source reachable-via rx” is configured on the ISP2 link to R1.
F.
“ip verify unicast source reachable-via any” is configured on the ISP2 link to R1.
Explanation:
ip verify unicast source reachable-via
To enable Unicast Reverse Path Forwarding (Unicast RPF), use the ip verify unicast source
reachable-via command in interface configuration mode. To disable Unicast RPF, use the no form
of this command.
ip verify unicast source reachable-via {rx | any} [allow-default] [allow-self-ping] [list] no ip verify
unicast source reachable-via
http://www.cisco.com/en/US/docs/ios/12_3/security/command/reference/sec_i2g.html#wp1103740
