RE: Telnet on port 179

From: Scott M Vermillion (scott_ccie_list@it-ag.com)
Date: Thu Oct 23 2008 - 01:37:49 ARST

>To clarify, remember BGP is an application. Not a protocol.

True, but some application needs to inform the TCP/IP stack to begin
listening on port 179, no?

SW2#sh ip bgp summ
% BGP not active

SW1#debug ip tcp transaction
TCP special event debugging is on
SW1#telnet 1.0.0.2 179
Trying 1.0.0.2, 179 ...
% Connection refused by remote host

SW1#
*Mar 3 04:00:56.861: TCB0379E9BC created
*Mar 3 04:00:56.869: TCB0379E9BC setting property TCP_VRFTABLEID (15)
37A3F04
*Mar 3 04:00:56.869: TCB0379E9BC setting property TCP_TOS (1) 37A3E60
*Mar 3 04:00:56.869: TCP: Random local port generated 26841, network 1
*Mar 3 04:00:56.869: TCB0379E9BC bound to 0.0.0.0.26841
*Mar 3 04:00:56.869: TPA: Reserved port 26841 in Transport Port Agent for
TCP IP type 1
*Mar 3 04:00:56.869: TCP: sending SYN, seq 1950560252, ack 0
*Mar 3 04:00:56.869: TCP0: Connection to 1.0.0.2:179, advertising MSS 1460
*Mar 3 04:00:56.869: TCP0: state was CLOSED -> SYNSENT [26841 ->
1.0.0.2(179)]
*Mar 3 04:00:56.869: TCP0: state was SYNSENT -> CLOSED [26841 ->
1.0.0.2(179)]
*Mar 3 04:00:56.869: TPA: Released port 26841 in Transport Port Agent for
TCP IP pe 1
*Mar 3 04:00:56.869: TCP0: bad seg from 1.0.0.2 -- closing connection: port
26841 seq 0 ack 1950560253 rcvnxt 0 rcvwnd 0 len 0
>>>> *Mar 3 04:00:56.869: TCP0: connection closed - remote sent RST <<<<
*Mar 3 04:00:56.86
SW1#9: TCB 0x379E9BC destroyed

SW2(config)#router bgp 100
SW2(config-router)# neighbor 1.0.0.1 remote-as 100

SW1#telnet 1.0.0.2 179
Trying 1.0.0.2, 179 ... Open

*Mar 3 04:04:38.571: TCB0379E9BC created
*Mar 3 04:04:38.571: TCB0379E9BC setting property TCP_VRFTABLEID (15)
37A3F04
*Mar 3 04:04:38.571: TCB0379E9BC setting property TCP_TOS (1) 37A3E60
*Mar 3 04:04:38.571: TCP: Random local port generated 60352, network 1
*Mar 3 04:04:38.571: TCB0379E9BC bound to 0.0.0.0.60352
*Mar 3 04:04:38.571: TPA: Reserved port 60352 in Transport Port Agent for
TCP IP type 1
*Mar 3 04:04:38.571: TCP: sending SYN, seq 2332155577, ack 0
*Mar 3 04:04:38.571: TCP0: Connection to 1.0.0.2:179, advertising MSS 1460
*Mar 3 04:04:38.571: TCP0: state was CLOSED -> SYNSENT [60352 ->
1.0.0.2(179)]
*Mar 3 04:04:38.580: TCP0: state was SYNSENT -> ESTAB [60352 ->
1.0.0.2(179)]
*Mar 3 04:04:38.580: TCP0: tcb 379E9BC connection to 1.0.0.2:179, received
MSS 1460, MSS is 1460
*Mar 3 04:04:38.580: TCB0379E9BC connected to 1.0.0.2.179

-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Charles Henson
Sent: Wednesday, October 22, 2008 6:56 PM
To: Mahesh Shivaswamy; Hobbs; Cisco certification
Subject: Re: Telnet on port 179

To clarify, remember BGP is an application. Not a protocol. So if you
telnet to 179 and get a RST on the TCP 3 way handshake, then none of
the BGP related functions have anything to do at this point. Not sure
if ACLs filtering you would send a RST. I thought they just dropped
you and the remote end timed out but I could be mistaken. Again, if
I'm mis-stating anything please let me know.

On 10/22/08, Charles Henson <chenson@gmail.com> wrote:
> I believe if you sent an RST then you are not listening on 179. Else
> you would have completed the 3 way handshake and then failed on the
> protocol. Someone correct me if I'm wrong here.
>
>
> On 10/22/08, Mahesh Shivaswamy <maheshs.cisco@gmail.com> wrote:
>> I need to chk if SW1 is listening on port 179.
>>
>> rgds
>> Mahesh
>>
>>
>> On Wed, Oct 22, 2008 at 7:00 PM, Hobbs <deadheadblues@gmail.com> wrote:
>>
>>> what are you trying to test?
>>>
>>> On Wed, Oct 22, 2008 at 5:54 PM, Mahesh Shivaswamy <
>>> maheshs.cisco@gmail.com> wrote:
>>>
>>>> Hi,
>>>>
>>>> When I telnet on port 23 between R4 & SW1 its fine, but when I telnet
on
>>>> port 179 I get a connection refuse msg, there is no access list on SW1.
>>>>
>>>> R4#telnet 154.1.47.7
>>>> Trying 154.1.47.7 ... Open
>>>>
>>>>
>>>> User Access Verification
>>>>
>>>> Password:
>>>>
>>>> R4#telnet 154.1.47.7 179
>>>> Trying 154.1.47.7, 179 ...
>>>> % Connection refused by remote host
>>>>
>>>> SW1#
>>>> 1d11h: tcp0: I LISTEN 154.1.47.4:18645 154.1.47.7:179 seq 2990396955
>>>> OPTS 4 SYN WIN 4128
>>>> 1d11h: TCP: sent RST to 154.1.47.4:18645 from 154.1.47.7:179
>>>>
>>>> SW1#sh run int vlan 47
>>>> Building configuration...
>>>>
>>>> Current configuration : 61 bytes
>>>> !
>>>> interface Vlan47
>>>> ip address 154.1.47.7 255.255.255.0
>>>> end
>>>>
>>>> Any suggestion what is the issue, this is the only way I can test, any
>>>> suggestion ?
>>>>
>>>> rgds
>>>> Mahesh
>>>>
>>>>
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>
>
> --
> Charles
> 

-- 
Charles

Blogs and organic groups at http://www.ccie.net

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