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Home > Archive > alt.certification.cisco > September 2003 > CCNA Cert Question (Wendel Odom)
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CCNA Cert Question (Wendel Odom)
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| Henrik Kern 2003-09-07, 4:28 pm |
| Hi all,
i'm preparing for the old CCNA Exam with the Cert Guide from Wendel Odom.
One Question is about spilt-horizon. The question goes something like this:
What is the default status about split-horizon on a serial interface
with no point-to-point subinterfaces?
The right answer according the Cert Guide is DISABLED.
When i made my labtesting, (using no p2p-subinfaces, leaving the serial
interfaces as it is regarding split horizon), I never saw networks
advertised that interface, which they are learned from, which means to
me: split-horizon is enabled by default!!!
Am i wrong???
Henrik
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| If I remember this right from Wendell Odom's book, Split Horizon is disabled
by default on FRAME RELAY interfaces and multipoint subinterfaces. It's not
disabled on point-to-point interfaces or subinterfaces. When you did your
lab testing, you used point-to-point interfaces. They are different from
Frame Relay interfaces, which are multipoint.
Split Horizon is disabled on Frame Relay interfaces and multipoint
subinterfaces because they can have several DLCIs to remote routers. Lets
assume Router_A has two DLCIs: 100 to connect to Router_B and 200 to connect
to Router_C. If you enable Split Horizon on Router_A's interface serial 0,
then the updates from Router_B coming (on DLCI 100) into Router_A's
interface serial 0 will not be sent (on DLCI 200) out of Router_A's serial 0
interface to Router_C . Therefore, Router_C will not be able to reach
networks off Router_B (for example, Router_C will not be able to reach the
Ethernet off Router_B). Therefore, Split Horizon has to be disabled, which
is the default setting. The same is true for multipoint subinterfaces.
Grey
"Henrik Kern" <henrik.kern@arcor.de> wrote in message
news:bjg21m$in8lk$1@ID-203117.news.uni-berlin.de...
> Hi all,
>
> i'm preparing for the old CCNA Exam with the Cert Guide from Wendel Odom.
>
> One Question is about spilt-horizon. The question goes something like
this:
>
> What is the default status about split-horizon on a serial interface
> with no point-to-point subinterfaces?
>
> The right answer according the Cert Guide is DISABLED.
>
> When i made my labtesting, (using no p2p-subinfaces, leaving the serial
> interfaces as it is regarding split horizon), I never saw networks
> advertised that interface, which they are learned from, which means to
> me: split-horizon is enabled by default!!!
>
> Am i wrong???
>
> Henrik
>
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