Cisco CCNP and CCIE Study Notes

Consider two routers connected back-to-back via serial links with PPP encapsulation. The links are already up. You decide to configure STAC data compression on the link and so you enter configuration mode on the routers at either end and type in compress stac under the interface configuration.

However, when you then issue a show compress command you see that compression is not enabled. Here is the output from one router

R1#sh runn int s 2
Building configuration...

Current configuration : 112 bytes
!
interface Serial2
 ip address 10.10.10.1 255.255.255.0
 encapsulation ppp
 no keepalive
 compress stac
end

R1# show compress
 Serial2
         Compression not active
         uncompressed bytes xmt/rcv 0/0
         compressed   bytes xmt/rcv 0/0
         1  min avg ratio xmt/rcv 0.000/0.000
         5  min avg ratio xmt/rcv 0.000/0.000
         10 min avg ratio xmt/rcv 0.000/0.000
         no bufs xmt 0 no bufs rcv 0
         resyncs 0

What is the problem here? Why isn't compression getting enabled?

Given the following output from a show isis database command on a Cisco router, can you identify

1. the Designated Intermediate Systems (DIS) in the network
2. the hostname of the router where this command was issued

IS-IS Level-1 Link State Database:
LSPID                 LSP Seq Num  LSP Checksum  LSP Holdtime      ATT/P/OL
R2.00-00            * 0x0000008E   0xE8BB        819               1/0/0
R3.00-00              0x0000007C   0x710E        704               0/0/0
R4.00-00              0x00000079   0x3FD3        691               0/0/0
R5.00-00              0x00000076   0x0D99        879               0/0/0
R5.01-00              0x00000080   0xA481        644               0/0/0
IS-IS Level-2 Link State Database:
LSPID                 LSP Seq Num  LSP Checksum  LSP Holdtime      ATT/P/OL
R1.00-00              0x00000080   0x4DED        971               0/0/0
R2.00-00            * 0x0000007F   0xBCA2        732               0/0/0
R6.00-00              0x0000005A   0xFE20        838               0/0/0
R6.01-00              0x00000057   0xA2B2        717               0/0/0
R8.00-00              0x0000005A   0x6AE7        1048              0/0/0