RE: IP route to Null0? [7:66755]
Well loads of answers already, but my £0.02- Routes to null can be used to blackhole traffic with lower overhead that an ACL, but obviously with less granuality. You could also use routes to null for redistribution, I have used this in the case of EIGRP when I wanted to redistribute static routes into EIGRP but wanted to keep them as internal routes, added a route to null and then redisitributed it that way .. static routes the specifiy an interface as the next hop are redistributed as locally connected and this internal metrics. Lastly, and what it seems to be used for in your case is BGP summarisation. Say for eg you had various /26's in your routing table, we would want to summarize this out to the rest of the world as a single /24. BGP will only advertise routes that are present in your internal routing process. This to force the BGP process to advertise the larger /24 prefix, you have to manuall inject this route into your routing table by using the route to null? Emilia Lambros wrote: Though to answer your question :) Summarization means advertising the biggest network you choose/should advertise. If you had a /23 that was routed as 2 /24s in your network, you'd summarize those as a /23 on the way out of your network to keep the routing table smaller... You should probably do the same for your next /24 unless you can find a specific reason not to. It saves headaches with route dampening in the long run if nothing else :) -Original Message- From: Anil Gupte [mailto:[EMAIL PROTECTED] Sent: Friday, 4 April 2003 7:21 AM To: [EMAIL PROTECTED] Subject: Re: IP route to Null0? [7:66755] You are right, it is using BGP. What does summarization do? Do I need an identical statement for my new Class C? Thanx, Anil Gupte - Original Message - From: Karsten To: Anil Gupte ; Sent: Thursday, April 03, 2003 10:46 AM Subject: Re: IP route to Null0? [7:66755] Either a sloppy way to drop traffic for a /24, or bgp summarization using null routing. -Karsten On Thursday 03 April 2003 07:40 am, Anil Gupte wrote: I am trying to understand some IP route commands on our router. Several of them go to Null0 - what does that mean? For example, I have ip route xxx.xxx.xxx.0 255.255.255.0 Null0 200 What is this doing? I need to add another block of class Cs from the same provider. Do I need a similar statement to the above? Thanx for your help. Anil Gupte Nondisclosure violations to [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=66830t=66755 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: IP route to Null0? [7:66755]
Not sure what engine line cards you're running on your GSRs, but I've run into several a problems with ACLs on the GSR platform. It's not until you get to the E3 ISE or better LC where ACLs are handled reasonably. Three problems from memory: * E0 line cards run the ACLs off the LC CPU and not ASICs. Thus you need to monitor the LC CPU to make sure you're ACL processing isn't impacting forwarding performance. * E2 3xGE trident LC. At the IOS rev we had, the LC could only do ACLs in one direction on the LC (I think inbound). If you wanted to do an outbound ACL, the ACL was actually copied and executed on all other LCs.This of course caused problems (bug) on another LC. * Pre E3 LC, pick one: ACLs or netflow. I'd avoid ACLs if you can null route it. Karsten wrote: I'll clarify. On lower end cisco routers not running bgp, yes, it will save you some cpu cycles. But most of the routers I'm working on a day to day basis(12Ks, 10Ks, 7200s) are running full table and hardly get slowed by by acls. Not to mention the problems a null route (for the purpose of bit-bucketing) can do when your're using null routes for bgp. -Karsten On Thursday 03 April 2003 10:53 am, MADMAN wrote: Sloppy!? why?? Dave Karsten wrote: Either a sloppy way to drop traffic for a /24, or bgp summarization using null routing. -Karsten On Thursday 03 April 2003 07:40 am, Anil Gupte wrote: I am trying to understand some IP route commands on our router. Several of them go to Null0 - what does that mean? For example, I have ip route xxx.xxx.xxx.0 255.255.255.0 Null0 200 What is this doing? I need to add another block of class Cs from the same provider. Do I need a similar statement to the above? Thanx for your help. Anil Gupte Nondisclosure violations to [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=66832t=66755 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: IP route to Null0? [7:66755]
Not sure what engine line cards you're running on your GSRs, but I've run into several a problems with ACLs on the GSR platform. It's not until you get to the E3 ISE or better LC where ACLs are handled reasonably. Three problems from memory: * E0 line cards run the ACLs off the LC CPU and not ASICs. Thus you need to monitor the LC CPU to make sure you're ACL processing isn't impacting forwarding performance. * E2 3xGE trident LC. At the IOS rev we had, the LC could only do ACLs in one direction on the LC (I think inbound). If you wanted to do an outbound ACL, the ACL was actually copied and executed on all other LCs.This of course caused problems (bug) on another LC. * Pre E3 LC, pick one: ACLs or netflow. I'd avoid ACLs if you can null route it. Karsten wrote: I'll clarify. On lower end cisco routers not running bgp, yes, it will save you some cpu cycles. But most of the routers I'm working on a day to day basis(12Ks, 10Ks, 7200s) are running full table and hardly get slowed by by acls. Not to mention the problems a null route (for the purpose of bit-bucketing) can do when your're using null routes for bgp. -Karsten On Thursday 03 April 2003 10:53 am, MADMAN wrote: Sloppy!? why?? Dave Karsten wrote: Either a sloppy way to drop traffic for a /24, or bgp summarization using null routing. -Karsten On Thursday 03 April 2003 07:40 am, Anil Gupte wrote: I am trying to understand some IP route commands on our router. Several of them go to Null0 - what does that mean? For example, I have ip route xxx.xxx.xxx.0 255.255.255.0 Null0 200 What is this doing? I need to add another block of class Cs from the same provider. Do I need a similar statement to the above? Thanx for your help. Anil Gupte Nondisclosure violations to [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=66846t=66755 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: IP route to Null0? [7:66755]
You know your GSRs :). Yea I'm running almost all ISE LCs. For example on a particular one at PAIX that averages about a half or a Gig during peak on almost all of my interfaces I have at least some type of acl in both directions. I only see about 8% cpu useage, hardly any of which is the ACL (mostly bgp). -Karsten On Friday 04 April 2003 03:49 am, bergenpeak wrote: Not sure what engine line cards you're running on your GSRs, but I've run into several a problems with ACLs on the GSR platform. It's not until you get to the E3 ISE or better LC where ACLs are handled reasonably. Three problems from memory: * E0 line cards run the ACLs off the LC CPU and not ASICs. Thus you need to monitor the LC CPU to make sure you're ACL processing isn't impacting forwarding performance. * E2 3xGE trident LC. At the IOS rev we had, the LC could only do ACLs in one direction on the LC (I think inbound). If you wanted to do an outbound ACL, the ACL was actually copied and executed on all other LCs.This of course caused problems (bug) on another LC. * Pre E3 LC, pick one: ACLs or netflow. I'd avoid ACLs if you can null route it. Karsten wrote: I'll clarify. On lower end cisco routers not running bgp, yes, it will save you some cpu cycles. But most of the routers I'm working on a day to day basis(12Ks, 10Ks, 7200s) are running full table and hardly get slowed by by acls. Not to mention the problems a null route (for the purpose of bit-bucketing) can do when your're using null routes for bgp. -Karsten On Thursday 03 April 2003 10:53 am, MADMAN wrote: Sloppy!? why?? Dave Karsten wrote: Either a sloppy way to drop traffic for a /24, or bgp summarization using null routing. -Karsten On Thursday 03 April 2003 07:40 am, Anil Gupte wrote: I am trying to understand some IP route commands on our router. Several of them go to Null0 - what does that mean? For example, I have ip route xxx.xxx.xxx.0 255.255.255.0 Null0 200 What is this doing? I need to add another block of class Cs from the same provider. Do I need a similar statement to the above? Thanx for your help. Anil Gupte Nondisclosure violations to [EMAIL PROTECTED] Nondisclosure violations to [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=66882t=66755 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: IP route to Null0? [7:66755]
What's sloppy about it ? Would you prefer the overhead of an acl ? Please suggest a better way.. But with the AD in there set to 200, it looks like a route in a holding pattern for bgp redistribution. Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=66759t=66755 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: IP route to Null0? [7:66755]
Either a sloppy way to drop traffic for a /24, or bgp summarization using null routing. -Karsten On Thursday 03 April 2003 07:40 am, Anil Gupte wrote: I am trying to understand some IP route commands on our router. Several of them go to Null0 - what does that mean? For example, I have ip route xxx.xxx.xxx.0 255.255.255.0 Null0 200 What is this doing? I need to add another block of class Cs from the same provider. Do I need a similar statement to the above? Thanx for your help. Anil Gupte Nondisclosure violations to [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=66757t=66755 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: IP route to Null0? [7:66755]
Sloppy!? why?? Dave Karsten wrote: Either a sloppy way to drop traffic for a /24, or bgp summarization using null routing. -Karsten On Thursday 03 April 2003 07:40 am, Anil Gupte wrote: I am trying to understand some IP route commands on our router. Several of them go to Null0 - what does that mean? For example, I have ip route xxx.xxx.xxx.0 255.255.255.0 Null0 200 What is this doing? I need to add another block of class Cs from the same provider. Do I need a similar statement to the above? Thanx for your help. Anil Gupte Nondisclosure violations to [EMAIL PROTECTED] -- David Madland CCIE# 2016 Sr. Network Engineer Qwest Communications 612-664-3367 I would rather have a German division in front of me than a French one behind me. --- General George S. Patton Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=66773t=66755 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: IP route to Null0? [7:66755]
null0 is used as an alternative to access-lists. it is a blackhole. so anything routed to it gets dropped automatically. an access-list uses more processor overhead than a null interface and thus if you have a certain part of your network that you don't want to go anywhere, then use a null interface instead of access-lists. as for why its a floating route or the tie-ins to bgp, thats beyond me and hopefully someone comments on this. bgp makes my head hurt. scott Anil Gupte wrote in message news:[EMAIL PROTECTED] I am trying to understand some IP route commands on our router. Several of them go to Null0 - what does that mean? For example, I have ip route xxx.xxx.xxx.0 255.255.255.0 Null0 200 What is this doing? I need to add another block of class Cs from the same provider. Do I need a similar statement to the above? Thanx for your help. Anil Gupte Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=66790t=66755 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: IP route to Null0? [7:66755]
I'll clarify. On lower end cisco routers not running bgp, yes, it will save you some cpu cycles. But most of the routers I'm working on a day to day basis(12Ks, 10Ks, 7200s) are running full table and hardly get slowed by by acls. Not to mention the problems a null route (for the purpose of bit-bucketing) can do when your're using null routes for bgp. -Karsten On Thursday 03 April 2003 10:53 am, MADMAN wrote: Sloppy!? why?? Dave Karsten wrote: Either a sloppy way to drop traffic for a /24, or bgp summarization using null routing. -Karsten On Thursday 03 April 2003 07:40 am, Anil Gupte wrote: I am trying to understand some IP route commands on our router. Several of them go to Null0 - what does that mean? For example, I have ip route xxx.xxx.xxx.0 255.255.255.0 Null0 200 What is this doing? I need to add another block of class Cs from the same provider. Do I need a similar statement to the above? Thanx for your help. Anil Gupte Nondisclosure violations to [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=66789t=66755 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: IP route to Null0? [7:66755]
You are right, it is using BGP. What does summarization do? Do I need an identical statement for my new Class C? Thanx, Anil Gupte - Original Message - From: Karsten To: Anil Gupte ; Sent: Thursday, April 03, 2003 10:46 AM Subject: Re: IP route to Null0? [7:66755] Either a sloppy way to drop traffic for a /24, or bgp summarization using null routing. -Karsten On Thursday 03 April 2003 07:40 am, Anil Gupte wrote: I am trying to understand some IP route commands on our router. Several of them go to Null0 - what does that mean? For example, I have ip route xxx.xxx.xxx.0 255.255.255.0 Null0 200 What is this doing? I need to add another block of class Cs from the same provider. Do I need a similar statement to the above? Thanx for your help. Anil Gupte Nondisclosure violations to [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=66797t=66755 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: IP route to Null0? [7:66755]
Though to answer your question :) Summarization means advertising the biggest network you choose/should advertise. If you had a /23 that was routed as 2 /24s in your network, you'd summarize those as a /23 on the way out of your network to keep the routing table smaller... You should probably do the same for your next /24 unless you can find a specific reason not to. It saves headaches with route dampening in the long run if nothing else :) -Original Message- From: Anil Gupte [mailto:[EMAIL PROTECTED] Sent: Friday, 4 April 2003 7:21 AM To: [EMAIL PROTECTED] Subject: Re: IP route to Null0? [7:66755] You are right, it is using BGP. What does summarization do? Do I need an identical statement for my new Class C? Thanx, Anil Gupte - Original Message - From: Karsten To: Anil Gupte ; Sent: Thursday, April 03, 2003 10:46 AM Subject: Re: IP route to Null0? [7:66755] Either a sloppy way to drop traffic for a /24, or bgp summarization using null routing. -Karsten On Thursday 03 April 2003 07:40 am, Anil Gupte wrote: I am trying to understand some IP route commands on our router. Several of them go to Null0 - what does that mean? For example, I have ip route xxx.xxx.xxx.0 255.255.255.0 Null0 200 What is this doing? I need to add another block of class Cs from the same provider. Do I need a similar statement to the above? Thanx for your help. Anil Gupte Nondisclosure violations to [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=66817t=66755 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: IP route to Null0? [7:66755]
In the event that you are running an internal dynamic routing protocol that would normally be the reason why the /24 is in your routing table (hence the ability for it to be in the BGP advertisements), should the place you are dynamically routing it to go away, so does your route in the IGP, thus so does the BGP route. Since providers dampen routes that flap constantly (to avoid their own routers being bogged down by BGP), if you have problems in your internal network, it is seen by other people. If your route gets dampened, certain parts of the internet can't get to you depending on who's done the dampening. (ie, if a route flaps, the router takes notice of how many times its flapped and when it hits a threshold, the route is removed from that provider's routing table for a specified period of time, usually depending on the size of network .. small /24's go for a long time because they're usually smaller outfits, /16 goes for a short period of time because its usually going to be a bigger outfit/tier 1). A route to null0 with a high AD provides a way for that route to exist in your IGP statically should your dynamic protocol have issues. You will never lose a route to Null0 unless you add it .. remove it .. add it .. remove it .. etc :) Or your router's having serious rebooting problems .. On the other hand, you'd also lose the route if it was a directly connected interface that went down. Null0 route would also help there I'd guess. -Original Message- From: Anil Gupte [mailto:[EMAIL PROTECTED] Sent: Friday, 4 April 2003 7:21 AM To: [EMAIL PROTECTED] Subject: Re: IP route to Null0? [7:66755] You are right, it is using BGP. What does summarization do? Do I need an identical statement for my new Class C? Thanx, Anil Gupte - Original Message - From: Karsten To: Anil Gupte ; Sent: Thursday, April 03, 2003 10:46 AM Subject: Re: IP route to Null0? [7:66755] Either a sloppy way to drop traffic for a /24, or bgp summarization using null routing. -Karsten On Thursday 03 April 2003 07:40 am, Anil Gupte wrote: I am trying to understand some IP route commands on our router. Several of them go to Null0 - what does that mean? For example, I have ip route xxx.xxx.xxx.0 255.255.255.0 Null0 200 What is this doing? I need to add another block of class Cs from the same provider. Do I need a similar statement to the above? Thanx for your help. Anil Gupte Nondisclosure violations to [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=66816t=66755 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
