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
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" <jsmith@vitalstream.com> To: <nanog@merit.edu> 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
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" <jsmith@vitalstream.com> To: <nanog@merit.edu> 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.
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" <jsmith@vitalstream.com> To: <nanog@merit.edu> 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 <matt@deliver3.com> "The Trouble with doing anything right the first time is that nobody appreciates how difficult it was." -BIX
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.
participants (5)
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Jean-Christophe Smith -
John Palmer -
Matt Levine -
Phil Rosenthal -
Sean Donelan