05-23-2012 08:29 AM - edited 03-04-2019 04:27 PM
Hi everyone,
We are connected to 2 different providers (PROV01 and PROV02) with eBGP full internet tables. PROV01 routes have higher local preference over PROV02.
We are having problems with our provider and would like your expertise. PROV01, higher preference has been having trouble with their router. The BGP remains up but the router stops forwarding traffic. as a resulta we lose connection to the internet but our traffic never goes to PROV02 since PROV01 BGP remains up announcing the 400K routes to us.
Is there a way to test internet connection though PROV01 and as the "internet is DOWN" automatically change traffic to PROV02? Can BGP parameters changes be triggered by IP SLA?
Our router is an ASR1006 RP2.
Thank you
05-23-2012 08:42 AM
You may use OER/PfR for direct BGP manipulation. IP SLA can't directly manipulate BGP, but you may tie some EEM script to IP SLA and do whatever you want inside that script.
05-25-2012 11:29 AM
Sergey,
Thanks for replying. I will be sincere and say I have never ever heard about what you wrote above.
Of course I can reserch further but can you please give us a brief introduction what these are and links for starting to use these them? OER?PfR?EEM?
Thank you.
05-26-2012 04:54 AM
OER is for Optimized Edge Routing, PfR is for Perfomance Routing, which are different names of the same technology. It is targeted to control perfomance of a particular routes and change them without changng or resetting all routing. This may be done automatically through BGP attributes (Local Preference) manipulation.
EEM is for Embeeded Event Manager. It is a scripting tool that allows for doing whatever you want (execute IOS command, send syslog or even e-mail, ...) in response to any event. Here your event might be tracking event triggered by IP SLA.
You also may use more tricky tools but they, probably, would be a combination of IP SLA, conditional routing etc.
You may find info about OER/PfR here: http://www.cisco.com/en/US/products/ps6628/products_ios_protocol_option_home.html
and about EEM here: http://www.cisco.com/en/US/products/ps6815/products_ios_protocol_group_home.html
05-30-2012 07:46 AM
Sergey,
Many thanks. Quick reading seems just the solution. Unfortunatelly I have a loooooooottt of reading to do.
I'll keep you posted on the results and configs (it may take some time because of all the studying and requesting testing windows)
Mario
05-30-2012 10:14 AM
It's a good chance to study something new OER is a rather complex technology and is not too fast. If you need a solution that reacts to changes in a few seconds, probably better to start from scripting. It is more simple. Don't dig into TCL scripting. This feature will allow you become a Router God but it will be a little later. Start from EEM applets.
05-30-2012 09:19 PM
Hi,
Apart from OER/PfR, you can also try BFD for the same.
More on BFD can be found on
http://www.cisco.com/en/US/docs/ios/12_0s/feature/guide/fs_bfd.html
HTH,
Smitesh
05-31-2012 02:30 AM
Smitesh,
Thanks but unfortunately from the "BFP Operation" we read:
BFD provides a low-overhead, short-duration method of detecting failures in the forwarding path between two adjacent routers, including the interfaces, data links, and forwarding planes. BFD is a detection protocol that you enable at the interface and routing protocol levels. Cisco supports the BFD asynchronous mode, which depends on the sending of BFD control packets between two systems to activate and maintain BFD neighbor sessions between routers. Therefore, in order for a BFD session to be created, you must configure BFD on both systems (or BFD peers). Once BFD has been enabled on the interfaces and at the router level for the appropriate routing protocols, a BFD session is created, BFD timers are negotiated, and the BFD peers will begin to send BFD control packets to each other at the negotiated interval.
From the bold parts we see that both devices would have to be neighbours and managed by us. Which is not the case. the next router is from the provider and communication stops 2 hops after that.
A method using ping woul be needed.
Thank you
05-31-2012 01:29 AM
Hi
this is very strange
because if the PE router stop pass traffic, and then a BGP session with other neighbors fall.
or it is mistake in provider network, just tell them about it.
I dont think you need here ip sla or something more. just make BGP whithout mistakes.
05-31-2012 02:36 AM
ttemirgaliye,
It is indeed a provider provider, they have been informed and admit it. Unfortunately no solution has been given until now and we have to find our own solution, avoid being woken up at night and keep service up for our customers.
Its a provider device and unfortunately not much help I can try to offer them on the causes of these.
Regards
MP
05-31-2012 03:02 AM
Hi
in this case ip sla may be simplest way.
just ping some router inside provider network
if no pings so shutdown interface to provider so BGP will switch all traffic to second provider.
for example
ip sla 10
icmp-echo 172.2.2.198 source-interface GigabitEthernet0/0
frequency 10
ip sla schedule 10 life forever start-time now
track 10 ip sla 10 reachability
delay down 20 up 20
!
event manager applet PE_down
event track 10 state down
action 1.0 syslog msg "PE_down"
action 2.0 -- conf t
action 3.0 -- int g0/0
action 4.0 -- shut
event manager applet PE_up
event track 10 state up
action 1.0 syslog msg "PE_up"
action 2.0
action 3.0
dont forget to rate post if it helps.
06-04-2012 04:01 AM
ttemirgaliye (whats your name?),
Thank you very helpfull indeed. I'm not familiar with EEM language (did not have time to read it yet) but looks simple to catch up.
One detail: How would this test the PE to be up if the source interface (g0/0 in your example) was shutdown? We would have to manually go in and "unshut" the interface bringing the problem momentarily to check.
Following your logic I came up with the following (considering we can configure/deconfigure static routes with EEM and the same ip sla as above)
event manager applet PE_down
event track 10 state down
action 1.0 syslog msg "PE_down"
action 2.0 -- conf t
action 3.0 -- add static route to PE2
event manager applet PE_up
event track 10 state up
action 1.0 syslog msg "PE_up"
action 2.0 -- conf t
action 3.0 -- remove static route to PE2
Let me know what you all think please
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