Re: Pitfalls of annoucing /24s
- Original Message - From: "Ejay Hire" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Friday, October 17, 2003 5:54 PM Subject: RE: Pitfalls of annoucing /24s > Am I the only one that has never had an issue multihoming with /24's? Nope, Most of the networks I've run are basically nothing but blocks of /24 announcements out of a larger /20 or whatever size block that has been assigned. In fact, it was alot easier for me to handle the network in that fashion, because I could easily control where traffic for a specific use came in, etc. -- Brian Bruns The Summit Open Source Development Group Open Solutions For A Closed World / Anti-Spam Resources http://www.sosdg.org ICQ: 8077511
RE: Pitfalls of annoucing /24s
Am I the only one that has never had an issue multihoming with /24's? Ejay Hire -Original Message- From: H. Michael Smith, Jr. [mailto:[EMAIL PROTECTED] Sent: Wednesday, October 15, 2003 4:24 PM To: 'Phil Rosenthal'; 'John Palmer' Cc: [EMAIL PROTECTED] Subject: RE: Pitfalls of annoucing /24s What about the /24's that many ISPs (especially tier 2-3) are assigning to multi-homed customers? What about an IX or "critical infrastructure providers" that may be issued a /24 from ARIN (Policy 2001-3)? Although it may be rare that a large aggregate would become unreachable to a "large" network, doesn't the possibility exist that a customer with a /24 would become unreachable (to some) due to the aggregate dropping out even though the /24 should still be reachable? That scenario may not be very likely, but the question of assymetric routing and one's ability to balance traffic become issues. Assigning a lower preference to /24's would be a lot friendlier than just throwing them away. If I am way off base, I fully expect to be corrected (with volume). My flame retardant suit is in place. Michael -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Phil Rosenthal Sent: Wednesday, October 15, 2003 4:47 PM To: John Palmer Cc: [EMAIL PROTECTED] Subject: Re: Pitfalls of annoucing /24s http://info.us.bb.verio.net/routing.html#PeerFilter That's how Verio does it, and I assume, that's how most people who filter by length do it as well. --Phil On Oct 15, 2003, at 4:40 PM, John Palmer wrote: > > Good question. > > You know there are thousands of legacy /24's out there that were > allocated by > IANA as /24's How can you aggregate them up if all you have is the /24? > > To those who filter out /24's - how is this done - just by the netmask > size? > > - Original Message - > From: "Jean-Christophe Smith" <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]> > Sent: Wednesday, October 15, 2003 15:34 > Subject: Pitfalls of annoucing /24s > > >> >> >> In current practice would there be serious jeopardy of portions of the >> internet not being able to reach this address space due to bgp >> filters or >> other restrictions? What is the smallest acceptable block of IPs that >> can be >> announced without adverse or unpredictable results? Verio would most >> likely >> be picking up these routes from us. I don't want to cause a religious >> debate, but I am interested in what the industry consensus is. >> >> I'm just doing some research, any comments would be appreciated. >> >> Thanks, >> Jean-Christophe Smith >> >> > > --Phil Rosenthal ISPrime, Inc.
Re: Pitfalls of annoucing /24s
Hello; On Wednesday, October 15, 2003, at 11:57 PM, Forrest wrote: True enough, but are there any providers currently that filter /24's from the old Class C space that /24's were assigned directly from? As someone who is multihomed but uses others /24's, I am sensitive to this. I do not _think_ that any major provider filters on /24's now - but it's fairly common to filter on /25 and longer. I realize that if proposal 2002-3 does get passed but everyone filters those prefixes then it will be a completely worthless proposal, and even worse than using PA space. I had good luck contacting the ISP's that were filtering and asking them nicely not to. I think that providers will mostly follow ARIN's lead. It seems to me that proposal 2002-3 could enable providers to filter more efficiently however. They could accept the long prefixes out of the micro-assignment block, while filtering out all the garbage /24's in the other space caused by people needlessly announcing every /24 out of their large aggregate. I would agree. Forrest Regards Marshall Eubanks On Wed, 15 Oct 2003, Andrew Dul wrote: Forrest, Even if ARIN passes this policy that will not make any provider change their filtering policy. It is true that many providers do use the ARIN allocation sizes to create their filtering rules but the two are not inherently linked. Any ASN can choose the filter on what ever rule set they choose. Andrew Regards Marshall Eubanks T.M. Eubanks e-mail : [EMAIL PROTECTED] http://www.multicasttech.com Test your network for multicast : http://www.multicasttech.com/mt/ Our New Video Service is in Beta testing http://www.americafree.tv
RE: Pitfalls of annoucing /24s
On 16 Oct 2003 at 9:44, McBurnett, Jim wrote: [...] > We are annoucing a /24 from the 66 /8 block and I have only found 2 ISP's > (according the the netlantis project) that can't reach me. > We are multihomed. I suspect that may be due to aggregation. > But even with our backup online, I still saw the routes propogate via > Netlantis.. > > Or am I out in left field going nuts? That's not bad at all. "Many" may be overstated. But if Charter announced a supernet around you those two dropouts should be able to reach you too. Better, eh? If your luck's anything like mine then the ones you lose are the ones you want. Peter E. Fry
RE: Pitfalls of annoucing /24s
->-Original Message- ->From: Phil Rosenthal [mailto:[EMAIL PROTECTED] ->As long as it's provider assigned, and your provider announces the ->supernet that the /24 is from, it will still work. If you ->announce PI ->space out of the old class A space in /24's, many networks ->wont be able ->to reach you. I am not sure I agree with this. We are annoucing a /24 from the 66 /8 block and I have only found 2 ISP's (according the the netlantis project) that can't reach me. We are multihomed. I suspect that may be due to aggregation. But even with our backup online, I still saw the routes propogate via Netlantis.. Or am I out in left field going nuts? Later, Jim
RE: Pitfalls of annoucing /24s
This is a part of the problem. I realize that large ISPs are probably against micro-assignments so that they can continue to use address space to treat customers as indentured servants. I guess they can skip Chicago and just filter out any micro-assignments that ARIN may one day issue. My biggest gripe on this topic is about ISPs that assign /24's to multi-homed customers, but filter out /24's received from peers. Verio (the example of the day) accepts /24's (that they likely assigned) from customers but filters these out from others. Are they expecting their peers not to filter these /24's or do they really care? I suppose if their peers adopt filtering policies such as theirs, they can just tell their customers "We accept your /24, but the other guy is filtering it out" Michael -Original Message- From: Andrew Dul [mailto:[EMAIL PROTECTED] Sent: Wednesday, October 15, 2003 11:35 PM To: Forrest; [EMAIL PROTECTED] Cc: [EMAIL PROTECTED] Subject: RE: Pitfalls of annoucing /24s Forrest, Even if ARIN passes this policy that will not make any provider change their filtering policy. It is true that many providers do use the ARIN allocation sizes to create their filtering rules but the two are not inherently linked. Any ASN can choose the filter on what ever rule set they choose. Andrew At 04:38 PM 10/15/2003 -0500, Forrest wrote: > > >This is just one of the many reasons why we need ARIN proposal 2002-3 to >be approved. So that small networks that wish to multihome don't have >issues with networks filtering out their /24 along with all the other >garbage /24's that are announced. > >http://www.arin.net/policy/2002_3.html > >If you support 2002-3 I urge you to get on the ARIN Public Policy >Mailing List (PPML) and voice your opinion. > >http://www.arin.net/mailing_lists/index.html > >Forrest > > >-Original Message- >From: H. Michael Smith, Jr. [SMTP:[EMAIL PROTECTED] >Sent: Wednesday, October 15, 2003 4:24 PM >To: 'Phil Rosenthal'; 'John Palmer' >Cc:[EMAIL PROTECTED] >Subject: RE: Pitfalls of annoucing /24s > > > >What about the /24's that many ISPs (especially tier 2-3) are assigning >to multi-homed customers? What about an IX or "critical infrastructure >providers" that may be issued a /24 from ARIN (Policy 2001-3)? > >Although it may be rare that a large aggregate would become unreachable >to a "large" network, doesn't the possibility exist that a customer with >a /24 would become unreachable (to some) due to the aggregate dropping >out even though the /24 should still be reachable? That scenario may >not be very likely, but the question of assymetric routing and one's >ability to balance traffic become issues. Assigning a lower preference >to /24's would be a lot friendlier than just throwing them away. > >If I am way off base, I fully expect to be corrected (with volume). My >flame retardant suit is in place. > >Michael > >-Original Message- >From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of >Phil Rosenthal >Sent: Wednesday, October 15, 2003 4:47 PM >To: John Palmer >Cc: [EMAIL PROTECTED] >Subject: Re: Pitfalls of annoucing /24s > > >http://info.us.bb.verio.net/routing.html#PeerFilter > >That's how Verio does it, and I assume, that's how most people who >filter by length do it as well. > >--Phil >On Oct 15, 2003, at 4:40 PM, John Palmer wrote: > >> >> Good question. >> >> You know there are thousands of legacy /24's out there that were >> allocated by >> IANA as /24's How can you aggregate them up if all you have is the >/24? >> >> To those who filter out /24's - how is this done - just by the netmask > >> size? >> >> - Original Message - >> From: "Jean-Christophe Smith" <[EMAIL PROTECTED]> >> To: <[EMAIL PROTECTED]> >> Sent: Wednesday, October 15, 2003 15:34 >> Subject: Pitfalls of annoucing /24s >> >> >>> >>> >>> In current practice would there be serious jeopardy of portions of >the >>> internet not being able to reach this address space due to bgp >>> filters or >>> other restrictions? What is the smallest acceptable block of IPs that > >>> can be >>> announced without adverse or unpredictable results? Verio would most >>> likely >>> be picking up these routes from us. I don't want to cause a religious >>> debate, but I am interested in what the industry consensus is. >>> >>> I'm just doing some research, any comments would be appreciated. >>> >>> Thanks, >>> Jean-Christophe Smith >>> >>> >> >> >--Phil Rosenthal >ISPrime, Inc. > > > > > > >
RE: Pitfalls of annoucing /24s
True enough, but are there any providers currently that filter /24's from the old Class C space that /24's were assigned directly from? I realize that if proposal 2002-3 does get passed but everyone filters those prefixes then it will be a completely worthless proposal, and even worse than using PA space. It seems to me that proposal 2002-3 could enable providers to filter more efficiently however. They could accept the long prefixes out of the micro-assignment block, while filtering out all the garbage /24's in the other space caused by people needlessly announcing every /24 out of their large aggregate. Forrest On Wed, 15 Oct 2003, Andrew Dul wrote: > Forrest, > > Even if ARIN passes this policy that will not make any provider change > their filtering policy. It is true that many providers do use the ARIN > allocation sizes to create their filtering rules but the two are not > inherently linked. Any ASN can choose the filter on what ever rule set > they choose. > > Andrew >
Re: Pitfalls of annoucing /24s
Hi Andy, Verio says they accept old class-a space at the /22 orshorter level so that isn't it. I am fairly certain you can not successfully multihome with PA class-A space.. If you are not announcing that /22 to AT&T then anyone that is single-homed to AT&T (or preferring them) will probably not be able to reach your /22. I ran into this problem with some 4/8 space that Level3 assigned to me by mistake. So you are dealing with more of a Policy issue rather than general prefix filter. -Scott - Original Message - From: "Andy Ellifson" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Wednesday, October 15, 2003 6:28 PM Subject: Re: Pitfalls of annoucing /24s > > I have a /24 allocated to my by XO Communications in Phoenix, AZ > (67.X.X.0/24). I am currently announcing it to Verio in Europe. A > friend of mine that is an XO customer in Phoenix with BGP to XO can get > to that address block within XO's network. > > But on the flip side. I also have a /22 from AT&T (12.X.X.0/22). When > I announce that network block to Verio in Europe (and nowhere else), > only certain places get to the Europe location. Networks that prefer > AT&T go to AT&T's network and die since the route isn't there. I don't > know if I am missing something but it think it may have to do with how > the network's peering/filter schemes work. > > I may just be walking around the problem since I am a transit customer > of Verio and they normally filter. > > -Andy > > > > --- Phil Rosenthal <[EMAIL PROTECTED]> wrote: > > > > On Oct 15, 2003, at 5:24 PM, H. Michael Smith, Jr. wrote: > > > > > > > > > > > What about the /24's that many ISPs (especially tier 2-3) are > > assigning > > > to multi-homed customers? What about an IX or "critical > > infrastructure > > > providers" that may be issued a /24 from ARIN (Policy 2001-3)? > > > > > As long as it's provider assigned, and your provider announces the > > supernet that the /24 is from, it will still work. If you announce > > PI > > space out of the old class A space in /24's, many networks wont be > > able > > to reach you. > > > > >
Re: Pitfalls of annoucing /24s
I have a /24 allocated to my by XO Communications in Phoenix, AZ (67.X.X.0/24). I am currently announcing it to Verio in Europe. A friend of mine that is an XO customer in Phoenix with BGP to XO can get to that address block within XO's network. But on the flip side. I also have a /22 from AT&T (12.X.X.0/22). When I announce that network block to Verio in Europe (and nowhere else), only certain places get to the Europe location. Networks that prefer AT&T go to AT&T's network and die since the route isn't there. I don't know if I am missing something but it think it may have to do with how the network's peering/filter schemes work. I may just be walking around the problem since I am a transit customer of Verio and they normally filter. -Andy --- Phil Rosenthal <[EMAIL PROTECTED]> wrote: > > On Oct 15, 2003, at 5:24 PM, H. Michael Smith, Jr. wrote: > > > > > > > What about the /24's that many ISPs (especially tier 2-3) are > assigning > > to multi-homed customers? What about an IX or "critical > infrastructure > > providers" that may be issued a /24 from ARIN (Policy 2001-3)? > > > As long as it's provider assigned, and your provider announces the > supernet that the /24 is from, it will still work. If you announce > PI > space out of the old class A space in /24's, many networks wont be > able > to reach you. >
RE: Pitfalls of annoucing /24s
Even if they understand it, why should they accept it? If an ISP assigns an address block, runs BGP with the customer, promotes multi-homing, shouldn't they make a reasonable effort to make it work? Unless I am missing something, I am having a big problem with an ISP assigning a /24 to a multi-homed customer and not accepting /24 routes. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of William Caban Sent: Wednesday, October 15, 2003 5:44 PM To: Jean-Christophe Smith Cc: NANOG Subject: RE: Pitfalls of annoucing /24s I will say most probably yes. I have seen this "problem"(?) on many small business customers. The hard part is trying to explain that to them. -William On Wed, 2003-10-15 at 17:16, Jean-Christophe Smith wrote: > I noticed the verio filter policy, in relation to inbound: > - In the traditional Class A space (i.e., 0/1), we accept /22 and shorter. > > If I want to announce a /24 in the 64.x.x.x space(traditional Class A space) > am I'm going to have a problem with other networks that have peer filters > similar to Verios? > > Thanks, > Jean-Christophe Smith -- William Caban <[EMAIL PROTECTED]>
RE: Pitfalls of annoucing /24s
Understood. But... networks filtering out the /24 announcement will always prefer the aggregate learned from the owner/issuer of the space. They'll be completely unaware that another route exists to the (/24) network. If the customers link to the provider that assigned the space goes down, those filtering /24's will still send the traffic to the 'owner' of the space (right?). What is the issuer of the /24 is filtering incoming /24 advertisements (Verio)? Will they learn the route to the other ISP or blackhole traffic destined for their own customer? I keep hoping that I am missing something here. If not, I sure hope more folks don't adopt Verio's filtering techniques. (I know that a VERY low AS # issues /24's out of a /8) -Original Message- From: Phil Rosenthal [mailto:[EMAIL PROTECTED] Sent: Wednesday, October 15, 2003 5:42 PM To: H. Michael Smith, Jr. Cc: [EMAIL PROTECTED]; 'John Palmer' Subject: Re: Pitfalls of annoucing /24s On Oct 15, 2003, at 5:24 PM, H. Michael Smith, Jr. wrote: > > > What about the /24's that many ISPs (especially tier 2-3) are assigning > to multi-homed customers? What about an IX or "critical infrastructure > providers" that may be issued a /24 from ARIN (Policy 2001-3)? > As long as it's provider assigned, and your provider announces the supernet that the /24 is from, it will still work. If you announce PI space out of the old class A space in /24's, many networks wont be able to reach you.
Re: Pitfalls of annoucing /24s
> "Phil" == Phil Rosenthal <[EMAIL PROTECTED]> writes: Phil> http://info.us.bb.verio.net/routing.html#PeerFilter Phil> That's how Verio does it, and I assume, that's how most people Phil> who filter by length do it as well. We currently see 28804 /24 prefixes from our transits and peers which are not more-specifics of another prefix that we see. (We see 127981 prefixes in total at the moment, so that's 22.5% of our table). By comparison, we see 41066 /24 prefixes which are more-specifics for another prefix, which is 32.1% of the table. In total, /24s account for 54.6% of the routes we see. Of those 28804 isolated /24 routes, 946 are in "class A" space (0-127), 604 are in "class B" space (128-191), and the remaining 27254 are in "class C" space (192-223). The detailed breakdown by /8 is: /8 |/24 routes | /24 routes |with aggr. | isolated |===|= 4 39 0 12722 0 13 1 0 15 6 0 16 1 0 17 2 0 20 5 1 24706117 25 0 1 32 94 0 38 50 0 40 23 0 43 1 0 44 2 0 55 1 0 57 11 0 61281 32 62360 82 63 1897 8 64 1693102 65 2012 2 66 1918250 67328 35 68381 13 69206 71 80218197 81233 31 82 15 4 128 68 26 129149 3 130 60 2 131 63 13 132 11 8 134107 5 135 6 4 136176 2 137 88 21 138 65 1 139 41 9 140131 1 141125 11 142 92 1 143 46 0 144 79 7 145 32 1 146145124 147 54 12 148287 4 149 68 11 150120 1 151 58 2 152219 2 153 57 1 154 7 0 155125 4 156 53 5 157 39 4 158139 1 159127 16 160 43 3 161 56 13 162182180 163 59 4 164111 14 165129 23 166 87 9 167285 19 168163 12 169 86 8 170298 17 171 8 0 192582 4767 193744 1703 194672 1326 195637639 196123350 198972 2499 199 1064 1763 200 1136 1877 201 1 0 202 1810 2229 203 1426 3775 204 1471 1488 205 1004 1028 206 1630453 207 2116370 208 2532 31 209 2294485 210761130 211320 60 212642275 213611360 214 15 0 215 22 0 216 2048 1203 217629424 218 95 16 219 33 0 220113 2 221 13 0 222 0 1 -- Andrew, Supernews
Re: Pitfalls of annoucing /24s
On Oct 15, 2003, at 4:46 PM, Phil Rosenthal wrote: http://info.us.bb.verio.net/routing.html#PeerFilter That's how Verio does it, and I assume, that's how most people who filter by length do it as well. Also worth noting that Verio does a loose-rpf check on their borders, so there's a possibility your packets will be dropped to multihomed customers who *do* have your /24 (if your best-path back to them is via verio.).. --Phil On Oct 15, 2003, at 4:40 PM, John Palmer wrote: Good question. You know there are thousands of legacy /24's out there that were allocated by IANA as /24's How can you aggregate them up if all you have is the /24? To those who filter out /24's - how is this done - just by the netmask size? - Original Message - From: "Jean-Christophe Smith" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Wednesday, October 15, 2003 15:34 Subject: Pitfalls of annoucing /24s In current practice would there be serious jeopardy of portions of the internet not being able to reach this address space due to bgp filters or other restrictions? What is the smallest acceptable block of IPs that can be announced without adverse or unpredictable results? Verio would most likely be picking up these routes from us. I don't want to cause a religious debate, but I am interested in what the industry consensus is. I'm just doing some research, any comments would be appreciated. Thanks, Jean-Christophe Smith --Phil Rosenthal ISPrime, Inc. -- Matt Levine <[EMAIL PROTECTED]> "The Trouble with doing anything right the first time is that nobody appreciates how difficult it was." -BIX
Re: Pitfalls of annoucing /24s
On Oct 15, 2003, at 5:24 PM, H. Michael Smith, Jr. wrote: What about the /24's that many ISPs (especially tier 2-3) are assigning to multi-homed customers? What about an IX or "critical infrastructure providers" that may be issued a /24 from ARIN (Policy 2001-3)? As long as it's provider assigned, and your provider announces the supernet that the /24 is from, it will still work. If you announce PI space out of the old class A space in /24's, many networks wont be able to reach you.
RE: Pitfalls of annoucing /24s
I will say most probably yes. I have seen this "problem"(?) on many small business customers. The hard part is trying to explain that to them. -William On Wed, 2003-10-15 at 17:16, Jean-Christophe Smith wrote: > I noticed the verio filter policy, in relation to inbound: > - In the traditional Class A space (i.e., 0/1), we accept /22 and shorter. > > If I want to announce a /24 in the 64.x.x.x space(traditional Class A space) > am I'm going to have a problem with other networks that have peer filters > similar to Verios? > > Thanks, > Jean-Christophe Smith -- William Caban <[EMAIL PROTECTED]>
RE: Pitfalls of annoucing /24s
This is just one of the many reasons why we need ARIN proposal 2002-3 to be approved. So that small networks that wish to multihome don't have issues with networks filtering out their /24 along with all the other garbage /24's that are announced. http://www.arin.net/policy/2002_3.html If you support 2002-3 I urge you to get on the ARIN Public Policy Mailing List (PPML) and voice your opinion. http://www.arin.net/mailing_lists/index.html Forrest -Original Message- From: H. Michael Smith, Jr. [SMTP:[EMAIL PROTECTED] Sent: Wednesday, October 15, 2003 4:24 PM To: 'Phil Rosenthal'; 'John Palmer' Cc: [EMAIL PROTECTED] Subject: RE: Pitfalls of annoucing /24s What about the /24's that many ISPs (especially tier 2-3) are assigning to multi-homed customers? What about an IX or "critical infrastructure providers" that may be issued a /24 from ARIN (Policy 2001-3)? Although it may be rare that a large aggregate would become unreachable to a "large" network, doesn't the possibility exist that a customer with a /24 would become unreachable (to some) due to the aggregate dropping out even though the /24 should still be reachable? That scenario may not be very likely, but the question of assymetric routing and one's ability to balance traffic become issues. Assigning a lower preference to /24's would be a lot friendlier than just throwing them away. If I am way off base, I fully expect to be corrected (with volume). My flame retardant suit is in place. Michael -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Phil Rosenthal Sent: Wednesday, October 15, 2003 4:47 PM To: John Palmer Cc: [EMAIL PROTECTED] Subject: Re: Pitfalls of annoucing /24s http://info.us.bb.verio.net/routing.html#PeerFilter That's how Verio does it, and I assume, that's how most people who filter by length do it as well. --Phil On Oct 15, 2003, at 4:40 PM, John Palmer wrote: > > Good question. > > You know there are thousands of legacy /24's out there that were > allocated by > IANA as /24's How can you aggregate them up if all you have is the /24? > > To those who filter out /24's - how is this done - just by the netmask > size? > > - Original Message - > From: "Jean-Christophe Smith" <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]> > Sent: Wednesday, October 15, 2003 15:34 > Subject: Pitfalls of annoucing /24s > > >> >> >> In current practice would there be serious jeopardy of portions of the >> internet not being able to reach this address space due to bgp >> filters or >> other restrictions? What is the smallest acceptable block of IPs that >> can be >> announced without adverse or unpredictable results? Verio would most >> likely >> be picking up these routes from us. I don't want to cause a religious >> debate, but I am interested in what the industry consensus is. >> >> I'm just doing some research, any comments would be appreciated. >> >> Thanks, >> Jean-Christophe Smith >> >> > > --Phil Rosenthal ISPrime, Inc.
Re: Pitfalls of annoucing /24s
On Wed, 15 Oct 2003, Jean-Christophe Smith wrote: > In current practice would there be serious jeopardy of portions of the > internet not being able to reach this address space due to bgp filters or > other restrictions? What is the smallest acceptable block of IPs that can be > announced without adverse or unpredictable results? The longest CIDR block that all ISPs accept is a /8. Anything longer than a /8 runs into some policy at some ISP. There are many rules of thumb about what is acceptable to a wide range of ISPs. Generally if you follow the number registry policies, and announce the block delegated directly from the registry most providers will accept it. Different address ranges have different historical CIDR lengths.
RE: Pitfalls of annoucing /24s
Don't know for certain, but I announce from time-time singular /24s out of my 64.x block (without announcing entire block, although at times I'd announce entire block as two /20s well) and have seen no problems with verio or anybody else. On Wed, 15 Oct 2003, Jean-Christophe Smith wrote: > > > I noticed the verio filter policy, in relation to inbound: > - In the traditional Class A space (i.e., 0/1), we accept /22 and shorter. > > If I want to announce a /24 in the 64.x.x.x space(traditional Class A space) > am I'm going to have a problem with other networks that have peer filters > similar to Verios? > > Thanks, > Jean-Christophe Smith > > -Original Message- > From: Phil Rosenthal [mailto:[EMAIL PROTECTED] > Sent: Wednesday, October 15, 2003 1:47 PM > To: John Palmer > Cc: [EMAIL PROTECTED] > Subject: Re: Pitfalls of annoucing /24s > > > http://info.us.bb.verio.net/routing.html#PeerFilter > > That's how Verio does it, and I assume, that's how most people who > filter by length do it as well. > > --Phil > On Oct 15, 2003, at 4:40 PM, John Palmer wrote: > > > > > Good question. > > > > You know there are thousands of legacy /24's out there that were > > allocated by > > IANA as /24's How can you aggregate them up if all you have is the /24? > > > > To those who filter out /24's - how is this done - just by the netmask > > size? > > > > - Original Message - > > From: "Jean-Christophe Smith" <[EMAIL PROTECTED]> > > To: <[EMAIL PROTECTED]> > > Sent: Wednesday, October 15, 2003 15:34 > > Subject: Pitfalls of annoucing /24s > > > > > >> > >> > >> In current practice would there be serious jeopardy of portions of the > >> internet not being able to reach this address space due to bgp > >> filters or > >> other restrictions? What is the smallest acceptable block of IPs that > >> can be > >> announced without adverse or unpredictable results? Verio would most > >> likely > >> be picking up these routes from us. I don't want to cause a religious > >> debate, but I am interested in what the industry consensus is. > >> > >> I'm just doing some research, any comments would be appreciated. > >> > >> Thanks, > >> Jean-Christophe Smith > >> > >> > > > > > --Phil Rosenthal > ISPrime, Inc.
RE: Pitfalls of annoucing /24s
What about the /24's that many ISPs (especially tier 2-3) are assigning to multi-homed customers? What about an IX or "critical infrastructure providers" that may be issued a /24 from ARIN (Policy 2001-3)? Although it may be rare that a large aggregate would become unreachable to a "large" network, doesn't the possibility exist that a customer with a /24 would become unreachable (to some) due to the aggregate dropping out even though the /24 should still be reachable? That scenario may not be very likely, but the question of assymetric routing and one's ability to balance traffic become issues. Assigning a lower preference to /24's would be a lot friendlier than just throwing them away. If I am way off base, I fully expect to be corrected (with volume). My flame retardant suit is in place. Michael -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Phil Rosenthal Sent: Wednesday, October 15, 2003 4:47 PM To: John Palmer Cc: [EMAIL PROTECTED] Subject: Re: Pitfalls of annoucing /24s http://info.us.bb.verio.net/routing.html#PeerFilter That's how Verio does it, and I assume, that's how most people who filter by length do it as well. --Phil On Oct 15, 2003, at 4:40 PM, John Palmer wrote: > > Good question. > > You know there are thousands of legacy /24's out there that were > allocated by > IANA as /24's How can you aggregate them up if all you have is the /24? > > To those who filter out /24's - how is this done - just by the netmask > size? > > - Original Message - > From: "Jean-Christophe Smith" <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]> > Sent: Wednesday, October 15, 2003 15:34 > Subject: Pitfalls of annoucing /24s > > >> >> >> In current practice would there be serious jeopardy of portions of the >> internet not being able to reach this address space due to bgp >> filters or >> other restrictions? What is the smallest acceptable block of IPs that >> can be >> announced without adverse or unpredictable results? Verio would most >> likely >> be picking up these routes from us. I don't want to cause a religious >> debate, but I am interested in what the industry consensus is. >> >> I'm just doing some research, any comments would be appreciated. >> >> Thanks, >> Jean-Christophe Smith >> >> > > --Phil Rosenthal ISPrime, Inc.
RE: Pitfalls of annoucing /24s
I noticed the verio filter policy, in relation to inbound: - In the traditional Class A space (i.e., 0/1), we accept /22 and shorter. If I want to announce a /24 in the 64.x.x.x space(traditional Class A space) am I'm going to have a problem with other networks that have peer filters similar to Verios? Thanks, Jean-Christophe Smith -Original Message- From: Phil Rosenthal [mailto:[EMAIL PROTECTED] Sent: Wednesday, October 15, 2003 1:47 PM To: John Palmer Cc: [EMAIL PROTECTED] Subject: Re: Pitfalls of annoucing /24s http://info.us.bb.verio.net/routing.html#PeerFilter That's how Verio does it, and I assume, that's how most people who filter by length do it as well. --Phil On Oct 15, 2003, at 4:40 PM, John Palmer wrote: > > Good question. > > You know there are thousands of legacy /24's out there that were > allocated by > IANA as /24's How can you aggregate them up if all you have is the /24? > > To those who filter out /24's - how is this done - just by the netmask > size? > > - Original Message - > From: "Jean-Christophe Smith" <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]> > Sent: Wednesday, October 15, 2003 15:34 > Subject: Pitfalls of annoucing /24s > > >> >> >> In current practice would there be serious jeopardy of portions of the >> internet not being able to reach this address space due to bgp >> filters or >> other restrictions? What is the smallest acceptable block of IPs that >> can be >> announced without adverse or unpredictable results? Verio would most >> likely >> be picking up these routes from us. I don't want to cause a religious >> debate, but I am interested in what the industry consensus is. >> >> I'm just doing some research, any comments would be appreciated. >> >> Thanks, >> Jean-Christophe Smith >> >> > > --Phil Rosenthal ISPrime, Inc.
Re: Pitfalls of annoucing /24s
http://info.us.bb.verio.net/routing.html#PeerFilter That's how Verio does it, and I assume, that's how most people who filter by length do it as well. --Phil On Oct 15, 2003, at 4:40 PM, John Palmer wrote: Good question. You know there are thousands of legacy /24's out there that were allocated by IANA as /24's How can you aggregate them up if all you have is the /24? To those who filter out /24's - how is this done - just by the netmask size? - Original Message - From: "Jean-Christophe Smith" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Wednesday, October 15, 2003 15:34 Subject: Pitfalls of annoucing /24s In current practice would there be serious jeopardy of portions of the internet not being able to reach this address space due to bgp filters or other restrictions? What is the smallest acceptable block of IPs that can be announced without adverse or unpredictable results? Verio would most likely be picking up these routes from us. I don't want to cause a religious debate, but I am interested in what the industry consensus is. I'm just doing some research, any comments would be appreciated. Thanks, Jean-Christophe Smith --Phil Rosenthal ISPrime, Inc.
Re: Pitfalls of annoucing /24s
Good question. You know there are thousands of legacy /24's out there that were allocated by IANA as /24's How can you aggregate them up if all you have is the /24? To those who filter out /24's - how is this done - just by the netmask size? - Original Message - From: "Jean-Christophe Smith" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Wednesday, October 15, 2003 15:34 Subject: Pitfalls of annoucing /24s > > > In current practice would there be serious jeopardy of portions of the > internet not being able to reach this address space due to bgp filters or > other restrictions? What is the smallest acceptable block of IPs that can be > announced without adverse or unpredictable results? Verio would most likely > be picking up these routes from us. I don't want to cause a religious > debate, but I am interested in what the industry consensus is. > > I'm just doing some research, any comments would be appreciated. > > Thanks, > Jean-Christophe Smith > >
