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Hi Guys,

i got a questions regarding loadbalancing on Cisco routers. say, I
have two locations( SiteA and SiteB) connected by two E1(LinkA, LinkB
of equal cost) Links and i am using load balancing on these two links.
i am using VoIP between Site A and Site B,so voice packets are also
routed via these two links. its everything ok if these two links are
stable. what happens when one of the links(say Link A) is
inconsistent. I mean if the LinkA is going up and down very frequently
( say for every 30 seconds), what happens to the voice packets?can the
packets that are routed on Link A reach their destination? i suppose,
if the packets are lost on link A, i can't ask the speaker to
reproduce the packets like how data packets are regenerated by their
applications, if they are lost. I think IOS maintains the route
corresponding to failed link for some period of time in its routing
table. what happenes to the voice packets routed via this particular
link A in the time between the link failure and the time of deletion
of route by IOS from its routing table?

how the IOS behaves in this situation and how the packets are routed
to destination and still using loadbalancing and EIGRP? how can I do
this?

any one plz help me.

regards
Manoj.

"Manoj Kumar Reddy" <> wrote in message
news: om...
> Hi Guys,
>
> i got a questions regarding loadbalancing on Cisco routers. say, I
> have two locations( SiteA and SiteB) connected by two E1(LinkA, LinkB
> of equal cost) Links and i am using load balancing on these two links.
> i am using VoIP between Site A and Site B,so voice packets are also
> routed via these two links. its everything ok if these two links are
> stable. what happens when one of the links(say Link A) is
> inconsistent.

Basically you are now running the most sensitive error detection protocol in
common use on a packet network (voip) - consistant packet loss, topology
changes etc will cause quality problems with voip before any conventional
data traffic problems show up.

I mean if the LinkA is going up and down very frequently
> ( say for every 30 seconds), what happens to the voice packets?can the
> packets that are routed on Link A reach their destination?

No - you have a "black hole" - packets sent that way are never seen again.

i suppose,
> if the packets are lost on link A, i can't ask the speaker to
> reproduce the packets like how data packets are regenerated by their
> applications, if they are lost. I think IOS maintains the route
> corresponding to failed link for some period of time in its routing
> table.

EIGRP runs recalcs on an event, but with a delay to dampen the number of
changes found

what happenes to the voice packets routed via this particular
> link A in the time between the link failure and the time of deletion
> of route by IOS from its routing table?

Gone.

You may want to look at LQM which can measure the reliability of a link and
take it out of service if it falls below a threshold.
http://www.cisco.com/en/US/products/...730a.html#3911
>
> how the IOS behaves in this situation and how the packets are routed
> to destination and still using loadbalancing and EIGRP? how can I do
> this?

I dont think EIGRP is the issue - the same stuff happens with any routing
protocol, in that some kinds of faults depend on a timeout, so there is a
delay between a fault and detection of a fault.
>
> any one plz help me.
>
> regards
> Manoj.
--
Regards

Stephen Hope - remove xx from email to reply

Manoj,

This issue came up last week on ccie groupstudy. There is a
mechanism

that you may want to take a look at called ip event dampening. Click below
to

learn about it.

http://www.cisco.com/en/US/products/...s_feature_guid
e09186a0080110bc8.html

I did not look very deeply into it but it looks like you can tune yout
routing protocol

to only install the route into the routing table if the interface is
well-behaved.

Good luck. Please let me know if this helps.


Jerry

"Manoj Kumar Reddy" <> wrote in message
news: om...
> Hi Guys,
>
> i got a questions regarding loadbalancing on Cisco routers. say, I
> have two locations( SiteA and SiteB) connected by two E1(LinkA, LinkB
> of equal cost) Links and i am using load balancing on these two links.
> i am using VoIP between Site A and Site B,so voice packets are also
> routed via these two links. its everything ok if these two links are
> stable. what happens when one of the links(say Link A) is
> inconsistent. I mean if the LinkA is going up and down very frequently
> ( say for every 30 seconds), what happens to the voice packets?can the
> packets that are routed on Link A reach their destination? i suppose,
> if the packets are lost on link A, i can't ask the speaker to
> reproduce the packets like how data packets are regenerated by their
> applications, if they are lost. I think IOS maintains the route
> corresponding to failed link for some period of time in its routing
> table. what happenes to the voice packets routed via this particular
> link A in the time between the link failure and the time of deletion
> of route by IOS from its routing table?
>
> how the IOS behaves in this situation and how the packets are routed
> to destination and still using loadbalancing and EIGRP? how can I do
> this?
>
> any one plz help me.
>
> regards
> Manoj.