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2 hops to ping myself?

 
Post new topic   Reply to topic    |##| -> |=|    MC MCSE Certification Forums -> CCENT/CCNA
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xunilhcra
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Joined: 30 Jul 2006
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Location: United States
Post subject: 2 hops to ping myself?
Posted: Thu Jan 04, 2007 8:53 pm		 Reply with quote

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I have connected two routers. The router that I use to issue the ping has an IP address of 68.43.52.100 and a default gateway of 68.43.52.1 (next-hop router). When I send an ICMP echo request packet to 68.43.52.100 (local router), it forwards it to the default gateway of 68.43.52.1! Then the default gateway sends back to me an ICMP bogus redirect message that says to forward my echo requests to 68.43.52.100, which is my local router. I was wondering why the router would be so silly to use the default gateway when the destination IP address is local.

Quote:
#show ip route
Gateway of last resort is 68.43.52.1 to network 0.0.0.0

68.0.0.0/24 is subnetted, 1 subnets
C 68.43.52.0 is directly connected, Serial0
C 192.168.1.0/24 is directly connected, Ethernet0
S* 0.0.0.0/0 [1/0] via 68.43.52.1
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kidvelvet
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Post subject:
Posted: Thu Jan 04, 2007 9:59 pm		 Reply with quote

Help others: Review your books and training products here
Could you post a sh run int se0 and a sh ip int brie?
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kidvelvet
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Yes, your problem is the most important. Just like everybody else's.
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xunilhcra
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Post subject:
Posted: Thu Jan 04, 2007 11:13 pm		 Reply with quote

Help others: Review your books and training products here
Sure.

Quote:
R1#show ip interface brief
Interface IP-Address OK? Method Status Protocol
Ethernet0 192.168.1.1 YES NVRAM up up

Serial0 68.43.52.100 YES NVRAM up up

Serial1 unassigned YES NVRAM administratively down down


Quote:
R1#show interface serial 0
Serial0 is up, line protocol is up
Hardware is HD64570
Internet address is 68.43.52.100/24
MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation HDLC, loopback not set
Keepalive set (10 sec)
Last input 00:00:09, output 00:00:03, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: weighted fair
Output queue: 0/1000/64/0 (size/max total/threshold/drops)
Conversations 0/1/256 (active/max active/max total)
Reserved Conversations 0/0 (allocated/max allocated)
Available Bandwidth 1158 kilobits/sec
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
14 packets input, 3175 bytes, 0 no buffer
Received 14 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
15 packets output, 1275 bytes, 0 underruns
0 output errors, 0 collisions, 3 interface resets
0 output buffer failures, 0 output buffers swapped out
4 carrier transitions
DCD=up DSR=up DTR=up RTS=up CTS=up
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waynoo
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Post subject:
Posted: Thu Jan 04, 2007 11:52 pm		 Reply with quote

Help others: Review your books and training products here
Can you post the command output of show run interface serial0

I would like to see the configuration of the whole interface

Thanks
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waynoo
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Post subject:
Posted: Thu Jan 04, 2007 11:55 pm		 Reply with quote

Help others: Review your books and training products here
Also you can try and delete your default static route and then try to ping yourself on serial0 and see what happens then

Very Happy
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Headhunter
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Post subject:
Posted: Fri Jan 05, 2007 1:44 am		 Reply with quote

Help others: Review your books and training products here
how are you connected to the router
what does debug ip packet say
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CCSI #30501 CCNP CCIP CCVP CCSP CCDP Cisco Advanced Wireless LAN Field Specialist Cisco Unity Design Specialist Cisco IP Telephony Design Specialist JNCIS-ES JNCIA-ER JNCIA-EX MCSE MCSA:Messaging
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war4years
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Post subject: Re: 2 hops to ping myself?
Posted: Fri Jan 05, 2007 2:39 am		 Reply with quote

Help others: Review your books and training products here
nevermind
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xunilhcra
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Joined: 30 Jul 2006
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Post subject:
Posted: Fri Jan 05, 2007 11:01 am		 Reply with quote

Help others: Review your books and training products here
The two routers are connected by a point-to-point DTE/DCE serial cable. The serial cable connects R1's S0 interface (68.43.52.100) to R2's S0 interface (68.43.52.1). I am issuing the IOS "ping" command while being consoled into R1.

Quote:
Gateway of last resort is 68.43.52.1 to network 0.0.0.0

68.0.0.0/24 is subnetted, 1 subnets
C 68.43.52.0 is directly connected, Serial0
C 192.168.1.0/24 is directly connected, Ethernet0
S* 0.0.0.0/0 [1/0] via 68.43.52.1


Quote:
R1#show run interface serial 0
Building configuration...

Current configuration : 80 bytes
!
interface Serial0
ip address 68.43.52.100 255.255.255.0
end


Removing the default static route from my IP routing table did not have an effect.

Quote:
R1#traceroute 68.43.52.100

Type escape sequence to abort.
Tracing the route to 68.43.52.100

1 68.43.52.1 16 msec 16 msec 16 msec
2 68.43.52.100 32 msec 32 msec *




Quote:
R1#debug ip packet
IP packet debugging is on

R1#ping 68.43.52.100

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 68.43.52.100, timeout is 2
!!!
*Mar 1 00:04:55.283: IP: tableid=0, s=68.43.52.100 (local), d=68.43.52.100 (Ser
ial0), routed via RIB
*Mar 1 00:04:55.287: IP: s=68.43.52.100 (local), d=68.43.52.100 (Serial0), len
100, sending
*Mar 1 00:04:55.319: IP: tableid=0, s=68.43.52.1 (Serial0), d=68.43.52.100 (Ser
ial0), routed via RIB
*Mar 1 00:04:55.323: IP: s=68.43.52.1 (Serial0), d=68.43.52.100 (Serial0), len
56, rcvd 3
*Mar 1 00:04:55.331: IP: tableid=0, s=68.43.52.100 (Serial0), d=68.43.52.100 (S
erial0), routed via RIB
*Mar 1 00:04:55.335: IP: s=68.43.52.100 (Serial0), d=68.43.52.100 (Serial0), le
n 100, rcvd 3
*Mar 1 00:04:55.343: IP: tableid=0, s=68.43.52.100 (local), d=68.43.52.100 (Ser
ial0), routed via RIB
*Mar 1 00:04:55.347: IP: s=68.43.52.100 (local), d=68.43.52.100 (Serial0), len
100, sending
*Mar 1 00:04:55.379: IP: tableid=0, s=68.43.52.100 (Serial0), d=68.43.52.100 (S
erial0), routed via RIB
*Mar 1 00:04:55.383: IP: s=68.43.52.100 (Serial0), d=68.43.52.100 (Serial0), le
n 100, rcvd 3
*Mar 1 !!
Success rate is 100 percent (5/5), round-trip min/avg/max = 96/109/144 ms
R1#00:04:55.391: IP: tableid=0, s=68.43.52.100 (local), d=68.43.52.100 (Serial0)
, routed via RIB
*Mar 1 00:04:55.395: IP: s=68.43.52.100 (local), d=68.43.52.100 (Serial0), len
100, sending
*Mar 1 00:04:55.431: IP: tableid=0, s=68.43.52.100 (Serial0), d=68.43.52.100 (S
erial0), routed via RIB
*Mar 1 00:04:55.435: IP: s=68.43.52.100 (Serial0), d=68.43.52.100 (Serial0), le
n 100, rcvd 3
*Mar 1 00:04:55.439: IP: tableid=0, s=68.43.52.100
ial0), routed via RIB
*Mar 1 00:04:55.443: IP: s=68.43.52.100 (local), d=68.43.52.100 (Serial0), len
100, sending
*Mar 1 00:04:55.479: IP: tableid=0, s=68.43.52.100 (Serial0), d=68.43.52.100 (S
erial0), routed via RIB
*Mar 1 00:04:55.483: IP: s=68.43.52.100 (Serial0), d=68.43.52.100 (Serial0), le
n 100, rcvd 3
*Mar 1 00:04:55.491: IP: tableid=0, s=68.43.52.100 (local), d=68.43.52.100 (Ser
ial0), routed via RIB
*Mar 1 00:04:55.495: IP: s=68.43.52.100 (local), d=68.43.52.100 (Serial0), len
100, sending
*Mar 1 00:04:55.531: IP: tableid=0, s=68.43.52.100 (Serial0), d=68.43.52.100 (S
Restricted Rights Legend

U
erial0), routed via RIBlosure by the Governmen
*Mar 1 00:04:55.535: IP: s=68.43.52.100 (Serial0), d=68.43.52.100 (Serial0), leas set forth in subparagraph
n 100, rcvd 3mmercial Comp
*Mar 1 00:04:55.539: IP: tableid=0, s=68.43.52.100 (local), d=68.43.52.100 (Serghts clause at FAR sec. 52.227-19 and subparagraph
ial0), routed via RIB
(c) (1) (ii) of the
*Mar 1 00:04:55.543: IP: s=68.43.52.100 (local), d=68.43.52.100 (Serial0), len
Software clause at DFARS sec. 252.227-7013.
100, sending


*Mar 1 00:04:55.579: IP: tableid=0, s=68.43.52.100 (Serial0), d=68.43.52.100 (Sasman Drive
San Jose, California 9513
erial0), routed via RIB
100, sending00
*Mar 1 00:04:55.675: IP: tableid=0, s=68.43.52.100 (Serial0), d=68.43.52.100 (S
*Mar 1 00:04:55.683: IP: tableid=0, s=68.43.52.100 (local), d=68.43.52.100 (Ser
ial0), routed via RIB
*Mar 1 00:04:55.687: IP: s=68.43.52.100 (local), d=68.43.52.100 (Serial0), len
100, sending
*Mar 1 00:04:55.723: IP: tableid=0, s=68.43.52.100 (Serial0), d=68.43.52.100 (S
erial0), routed via RIB
*Mar 1 00:04:55.727: IP: s=68.43.52.100 (Serial0), d=68.43.52.100 (Serial0), le
n 100, rcvd 3
*Mar 1 00:04:55.735: IP: tableid=0, s=68.43.52.100 (local), d=68.43.52.100 (Ser
ial0), routed via RIB
*Mar 1 00:04:55.739: IP: s=68.43.52.100 (local), d=68.43.52.100 (Serial0), len
100, sending
*Mar 1 00:04:55.775: IP: tableid=0, s=68.43.52.100 (Serial0), d=68.43.52.100 (S
erial0), routed via RIB
*Mar 1 00:04:55.779: IP: s=68.43.52.100 (Serial0), d=68.43.52.100 (Serial0), le
n 100, rcvd 3
*Mar 1 00:04:55.783: IP: tableid=0, s=68.43.52.100 (local), d=68.43.52.100 (Ser
ial0), routed via RIB
*Mar 1 00:04:55.787: IP: s=68.43.52.100 (local), d=68.43.52.100 (Serial0), len
100, sending
*Mar 1 00:04:55.823: IP: tableid=0, s=68.43.52.100 (Serial0), d=68.43.52.100 (S
erial0), routed via RIB
*Mar 1 00:04:55.827: IP: s=68.43.52.100 (Serial0), d=68.43.52.100 (Serial0), le
n 100, rcvd 3
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EireannX
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Post subject:
Posted: Mon Jan 08, 2007 1:23 am		 Reply with quote

Help others: Review your books and training products here
From http://www.cisco.com/univercd/cc/td/doc/product/software/ssr90/tsc_r90/54019.htm

Quote:
Note If the IP version of the ping command is used on a directly connected interface, the packet is sent out the interface and should be forwarded back to the router from the far end. The time travelled reflects this round trip route. This feature can be useful for diagnosing serial line problems. By placing the local or remote CSU/DSU into loopback mode and "pinging" your own interface, you can isolate the problem to the router or leased line.


Basically the packet is sent out the interface to perform the ping test. You will not notice it on a broadcast medium like Ethernet, as there is no intermediary hop, but on a point-to-point or NBMA medium you will need to have the far end route the packet back to you.
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