A. Attempt to TELNET from the router connected to the inside of the firewall to the router connected to the outside of the firewall. If telnet works， BGP will work， since telnet and BGP both use TCP to transport data.
B. Ping from the router connected to the inside interface of the firewall to the router connected to the outside interface of the firewall. If you can ping between them， BGP should work， since BGP uses IP to transport packets.
C. There is no way to make BGP work across a firewall without special configuration， so there is no simple test that will show you if BGP will work or not， other than trying to start the peering session.
D. There is no way to make BGP work across a firewall.

A.Change your Internet provider.
B.Change your public IP address.
C.Allow the email server to send traffic only to TCP port 25.
D.Put your email server in a DMZ.
E.Use a separate public IP address for your email server only.

A. Port 3/12 was already up and forwarding before the loop was created.
B. Port priority is based on lowest priority and lowest port number.
C. You connected the wire on port 3/18 last.
D. None of the above， it is purely random.

A.Increase memory allocation for ACLs.
B.Remove all entries from the ACL and use a single permit ip any any statement.
C.Remove the log keyword from each ACL entry.
D.Reboot the device after the ACL has been applied.

A. Only use fiber in pairs.
B. Configure root guard on your switches.
C. Do not use fiber but use copper.
D. Configure UDLD to prevent one-way link conditions.

A.IPSec VPN
B.SSL VPN
C.port security
D.port security with statically configured MAC addresses
E.private VLANs

A. Make HSRP track interfaces between the edge and core routers.
B. Replace HSRP with GLBP.  用GLBP替换HSRP
C. Add crossed intrasite links： R1-R4， R2-R3， R5-R8， and R6-R7.
D. Make R3 and R8 have lower HSRP priority than R1 and R7.
E. Replace HSRP with VRRP

A.root guard
B.loop guard
C.BPDU guard
D.UDLD
E.BPDU skew detection

A. Because Frame Relay IETF encapsulation is only configurable at interface level， you must use IETF encapsulation on all routers.
B. This is not a possible scenario. A dedicated Frame Relay link to RemoteB is mandatory at the central office.
C. The router at RemoteB must be replaced by a Cisco router.
D. Use Frame Relay IETF encapsulation on a per-VC basis on the central office router.
E. There is a problem in the Frame Relay cloud， because Cisco routers are compatible with IETF Frame Relay.

A.ip verify unicast source reachable-via any
B.ip verify unicast reverse-path
C.ip verify unicast reverse-path loose
D.ip verify unicast reverse-path strict