[isp-bgp] Re: Routing Information

[haesu@...]

	one thing you could do is..
	setup an IGP between the two routers that distribute static routes
	between the two. since floating static route to Null0 has a.d. of 254,
	IGP route will be preferred over 254 floating static., thereby sending
	traffic off to another router according to igp status during a failure.

	at the same time, your normal static route will take precedence over
	anything as long as you use the default/standard a.d. on it.

	this is just one of the many ways you can use to get around the problem.
	ofcourse, YMMV.

-J

-- 
James Jun (formerly Haesu)
TowardEX Technologies, Inc.
1740 Massachusetts Ave.
Boxborough, MA 01719
Consulting, IPv4 & IPv6 colocation, web hosting, network design & implementation
http://www.towardex.com  | james@towardex.com
Cell: (978)394-2867    
Fax: (978)263-0033       | AIM: GigabitEthernet0
NOC: http://www.twdx.net | POC: HAESU-ARIN, HDJ1-6BONE


On Sun, Feb 29, 2004 at 01:09:44AM -0500, Serge Paquin wrote:
> There is always a catch :)
> 
> How would I properly account for redundancy if I'm using HSRP?  2 routers, 2
> providers connected to an internal switch and connected to each other via
> crossover.
> 
> If a router looses conductivity to the switch along with the other router at
> the same time and still advertises it's routes there is a blackhole of
> sorts.
> 
> Am I just overanalyzing the problem?  I realize the chance of 2 Ethernet
> links going down at the same time while the Serial interface of the router
> is still working is very far fetched. Is it even reasonable to account for
> such an occurrence?
> 
> Serge.
> 
> ----- Original Message -----
> From: "James" <haesu@...>
> To: <isp-bgp@isp-bgp.com>
> Sent: Sunday, February 29, 2004 12:58 AM
> Subject: [isp-bgp] Re: Routing Information
> 
> 
> yes you are missing something.. :P
> 
> if the router doesnt see the route and drops the bgp advertisement..
> that's all fine and dandy... but...
> 
> now what happens if your ethernet starts flapping hard? you are going
> to start flapping bgp advertisements. now that might not be a problem
> for you if this is bgp over an internal network that does not propagate
> the advertisements to the internet.. but if this is a live bgp session
> with your upstream isp and what not, you are going to experience some
> serious dampening penalties after enough flaps.
> 
> flapping leads to dampening.
> dampening leads to suffering.
> 
> besides... if the route becomes unavailable, it can be safely routed to
> bitbucket anyway.
> 
> my 0.02
> 
> -J
> 
> --
> James Jun (formerly Haesu)
> TowardEX Technologies, Inc.
> 1740 Massachusetts Ave.
> Boxborough, MA 01719
> Consulting, IPv4 & IPv6 colocation, web hosting, network design &
> implementation
> http://www.towardex.com  | james@towardex.com
> Cell: (978)394-2867      | Office: (978)263-3399 Ext. 170
> Fax: (978)263-0033       | AIM: GigabitEthernet0
> NOC: http://www.twdx.net | POC: HAESU-ARIN, HDJ1-6BONE
> 
> On Sun, Feb 29, 2004 at 12:54:08AM -0500, Serge Paquin wrote:
> > Thanks for the quick reply.
> >
> > Actually I'm thinking about not having the floating route.  If the router
> > cannot see the internal switch and it's local neighbor router it has
> nowhere
> > to send the traffic so I figure it should not be advertising.
> >
> > I see everyone always recommending a floating route but I figure that
> could
> > give me a type of local blackhole.
> >
> > Am I missing something?
> >
> > Serge.
> >
> > ----- Original Message -----
> > From: "James" <haesu@...>
> > To: <isp-bgp@isp-bgp.com>
> > Sent: Sunday, February 29, 2004 12:49 AM
> > Subject: [isp-bgp] Re: Routing Information
> >
> >
> > >     If there is no static route to a locally BGP advertised block BGP
> will
> > > not advertise?
> >
> > correct.
> >
> > thats why you can either a) advertise a connected route or
> > b) set a floating static route.
> >
> > >     ie:
> > >     route1 advertises 192.168.0.0/24 via BGP
> >
> > i.e. do this:
> >
> > conf t
> > router bgp blah
> > network 192.168.0.0 mask 255.255.255.0
> > exit
> > ip route 192.168.0.0 255.255.255.0 192.168.1.1
> > ip route 192.168.0.0 255.255.255.0 192.168.2.1 50
> > ! The floating route to null.
> > ip route 192.168.0.0 255.255.255.0 Null0 254
> >
> > can also use 'permanent' as well.
> >
> > -J
> >
> > --
> > James Jun (formerly Haesu)
> > TowardEX Technologies, Inc.
> > 1740 Massachusetts Ave.
> > Boxborough, MA 01719
> > Consulting, IPv4 & IPv6 colocation, web hosting, network design &
> > implementation
> > http://www.towardex.com  | james@towardex.com
> > Cell: (978)394-2867
> > Fax: (978)263-0033       | AIM: GigabitEthernet0
> > NOC: http://www.twdx.net | POC: HAESU-ARIN, HDJ1-6BONE
> >
> > >
> > >     static route:
> > >     ip route 192.168.0.0 255.255.255.0 192.168.1.1
> > >     ip route 192.168.0.0 255.255.255.0 192.168.2.1 50
> > >
> > >     If the router looses it's like to the 192.168.1.0 and 192.168.2.0
> > > networks the static routes become invalid and theirfore the router will
> > stop
> > > advertising 192.168.0.0/24 via BGP?
> > >
> > > Thanks,
> > > Serge.
> > >
> > >
> > >




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