From: Victor Cappuccio (victor@ccbootcamp.com)
Date: Sat Jun 02 2007 - 23:44:47 ART
Upss sorry for the spam, I misted the post, please ignore the previews one
http://www.groupstudy.com/archives/ccielab/200608/msg00305.html
-----Original Message-----
From: nobody@groupstudy.com on behalf of Victor Cappuccio
Sent: Sat 6/2/2007 19:31
To: Tony Dubiel; Sadiq Yakasai; premkumar somasundaram
Cc: ccielab@groupstudy.com
Subject: RE: Reflexive access-list
More Reflexive ACL Configuration by Narbik @
http://www.groupstudy.com/archives/ccielab/200607/msg01647.html
:)
-----Original Message-----
From: nobody@groupstudy.com on behalf of Tony Dubiel
Sent: Sat 6/2/2007 19:16
To: Sadiq Yakasai; premkumar somasundaram
Cc: ccielab@groupstudy.com
Subject: RE: Reflexive access-list
dce-terminal-timing enable --- It is simply an option, that when enabled will
look for timing from the DTE device instead of the internal clock for a DCE
interface.
The documentation simply states it is needed for longer serial cables between
the DCE and DTE but doesn't give an exact cable length to consider this
option, in order to prevent phase shifting.
The DTE must send SCTE timing to allow the Router set up as a DCE to enable
this option.
External data port clocking
One way to address the problem of a phase-shifted clock signal is to change
the source of the transmit clock at the data port. Routers can be designed to
accept the transmit clock from the CSU/DSU and use it to drive the external
clock line. The external clock line is often labeled XCLK or SCTE (an
abbreviation for serial clock timing external). The router assumes the
responsibility of synchronizing the transmitted data with the external clock
signal. With external clocking, the clock and data must take the same path
and
are subject to the same delays, so the data and its clock signal stay in
phase
over the cable.
So for most home lab situations this option is never needed because there is
only a short cross over serial connection, which only requires one router to
be a DCE and provide the timing across the serial cable from its internal
clock.
Best Regards,
Tony Dubiel
Technical Instructor, CCIE#10844, CCSP, CISSP, AWLFS/DS (wireless)
Cisco Technical Solutions Specialist (TSS)
240-882-4304 Cell
Network Learning Inc - A Cisco Sponsored Organization (SO)YES! We take Cisco
Learning credits!
________________________________
From: nobody@groupstudy.com on behalf of Sadiq Yakasai
Sent: Sat 6/2/2007 9:43 AM
To: premkumar somasundaram
Cc: ccielab@groupstudy.com
Subject: Re: Reflexive access-list
Hi Guys,
Please whats the purpose of the "dce-terminal-timing-enable" command
on the serial interface?
Thanks
On 6/2/07, premkumar somasundaram <premkumar.somasundaram@gmail.com> wrote:
> Group.
> I have a issue with the reflexive access-list. Here is the scenario.... I
> need to configure reflexive access-list on R3 to allow ICMP, TCP, UDP and
> OSPF traffic from inside to outside. The configuration is follows.
>
>
> interface Serial2/3
> ip address 136.1.23.3 255.255.255.0
> ip access-group INBOUND in
> ip access-group OUTBOUND out
> encapsulation ppp
> clock rate 64000
> no dce-terminal-timing-enable
>
>
> ip access-list extended INBOUND
> evaluate MIRROR
> ip access-list extended OUTBOUND
> permit icmp any any reflect MIRROR
> permit tcp any any reflect MIRROR
> permit udp any any reflect MIRROR
> permit ospf any any reflect MIRROR
> !
>
> For testing, I used to ping for ICMP, Telnet for TCP , and Routing protocol
> for OSPF.
>
> But none of them worked...I am sure something is missing from the config
> which i could nt find out..can any one help me on this...
>
>
> Thanks
> Prem
>
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