Re: IERS Lab4 Task1.3 - Loopguard and UDLD

There are some difference in both although they have functionality overlap.
But still some difference exist.

1- Loop Guard can be configured per port and per vlan basis, but UDLD cannot
be, its only per port feature.
2- STP can detect failures in STP software (although a rare possibility, but
still a possibility).
3- There is difference between these two for recovery too. UDLD enabled port
can only recover if err-disable timeout is enabled.

HTH

On Sun, Jan 24, 2010 at 8:01 PM, Michael McFarlin <router.genie_at_gmail.com>wrote:

> Nadeem
>
> When configured as
>
> (config)# udld {enable|aggressive)
> only affects fiber ports
>
> (config-if)# udld port aggressive
> can be used on fiber ports or copper links.
>
> The aggressive option forces the link to shut down when a unidirectional
> link is detected. So why worry about using loopguard?
>
> Thanks
>
> -Mike
>
> On Sun, Jan 24, 2010 at 8:49 AM, Nadeem Rafi <nrafia_at_gmail.com> wrote:
>
>> What i know, UDLD is basically developed for Fiber optics, where chance of
>> one way communication are more than any thing else. And UDLD uses its own
>> mechanism to detected unidirectional links.
>>
>> Where as LoopGuard uses STP mechanism to detect unidirectional links and
>> mostly enabled for copper links.
>>
>> HTH
>>
>> On Sun, Jan 24, 2010 at 3:05 PM, Michael McFarlin <router.genie_at_gmail.com
>> > wrote:
>>
>>> Experts,
>>>
>>> I have a question about UDLD and Loopguard in one of the IERS labs. I
>>> don't
>>> think that loopguard is needed at all here. Why would you have to worry
>>> about SW1 making the Fa0/15 a designated port if UDLD has already taken
>>> the
>>> port down? By default UDLD acts faster than Loopguard by default right?
>>>
>>>
>>> Task
>>>
>>> Administrators of your network are concerned about SW1 and SW2 not
>>> being able to detect a link failure on port Fa0/15.
>>>
>>> Configure SW1 and SW2 so that port Fa0/15 is brought down in the case
>>> that either switch can send traffic, but not receive, or vice versa.
>>>
>>> As an additional precaution, configure SW1 so that interface Fa0/15 is
>>> not
>>> mistakenly elected as a designated port in the above case.
>>>
>>> Answer
>>>
>>> SW1:
>>> interface FastEthernet0/15
>>> udld port aggressive
>>> spanning-tree guard loop
>>> SW2:
>>> interface FastEthernet0/15
>>> udld port aggressive
>>>
>>>
>>> -Mike
>>>
>>>
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>>>
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>>
>
>
> --
> Mike McFarlin
> router.genie_at_gmail.com

Blogs and organic groups at http://www.ccie.net
Received on Sun Jan 24 2010 - 20:08:16 ART