Re: /31 subnet (now with info link) [7:27802]
With a /30 you use 4 IP addresses (network, 2 node, 1 broadcast). You save addresses with a /31. Here's a link with more info: http://www.ietf.org/rfc/rfc3021.txt?number=3021 Thanks, Craig At 08:32 AM 11/30/2001 -0500, you wrote: Maybe I'm missing something, but there are only 2 useable addresses in a /30, and only 2 interfaces participating in a point-to-point link, so how are there 50% of the addresses wasted. Steve MADMAN wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... Point to point connections, with a /30 you waste 50% of the avaivalable addresses. Dave Nicolas FEVRIER wrote: Hi group, I'm puzzled by the use of /31 subnets... Anybody can explain me the benefits of such a subnet on an interface ? Thanxx. Nicolas. -- David Madland Sr. Network Engineer CCIE# 2016 Qwest Communications Int. Inc. [EMAIL PROTECTED] 612-664-3367 Emotion should reflect reason not guide it Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=27802t=27802 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: /31 subnet (now with info link) [7:27802]
I know that, but the network and broadcast addresses are unusable. Thus the two good addresses for hosts. Craig Columbus wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... With a /30 you use 4 IP addresses (network, 2 node, 1 broadcast). You save addresses with a /31. Here's a link with more info: http://www.ietf.org/rfc/rfc3021.txt?number=3021 Thanks, Craig At 08:32 AM 11/30/2001 -0500, you wrote: Maybe I'm missing something, but there are only 2 useable addresses in a /30, and only 2 interfaces participating in a point-to-point link, so how are there 50% of the addresses wasted. Steve MADMAN wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... Point to point connections, with a /30 you waste 50% of the avaivalable addresses. Dave Nicolas FEVRIER wrote: Hi group, I'm puzzled by the use of /31 subnets... Anybody can explain me the benefits of such a subnet on an interface ? Thanxx. Nicolas. -- David Madland Sr. Network Engineer CCIE# 2016 Qwest Communications Int. Inc. [EMAIL PROTECTED] 612-664-3367 Emotion should reflect reason not guide it Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=27803t=27802 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: /31 subnet (now with info link) [7:27802]
I read the RFC, so I guess it can be used. My bad. AM I correct in saying that one interface will be assigned the all zero subnet as it's IP and the other will be assigned the broadcast IP address for that subnet? Steve VoIP Guy wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... I know that, but the network and broadcast addresses are unusable. Thus the two good addresses for hosts. Craig Columbus wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... With a /30 you use 4 IP addresses (network, 2 node, 1 broadcast). You save addresses with a /31. Here's a link with more info: http://www.ietf.org/rfc/rfc3021.txt?number=3021 Thanks, Craig At 08:32 AM 11/30/2001 -0500, you wrote: Maybe I'm missing something, but there are only 2 useable addresses in a /30, and only 2 interfaces participating in a point-to-point link, so how are there 50% of the addresses wasted. Steve MADMAN wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... Point to point connections, with a /30 you waste 50% of the avaivalable addresses. Dave Nicolas FEVRIER wrote: Hi group, I'm puzzled by the use of /31 subnets... Anybody can explain me the benefits of such a subnet on an interface ? Thanxx. Nicolas. -- David Madland Sr. Network Engineer CCIE# 2016 Qwest Communications Int. Inc. [EMAIL PROTECTED] 612-664-3367 Emotion should reflect reason not guide it Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=27806t=27802 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: /31 subnet (now with info link) [7:27802]
Just tried it and the router dosen't even allow an interface to use a /31 mask, even with ip subnet-zero enabled. VoIP Guy wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... I read the RFC, so I guess it can be used. My bad. AM I correct in saying that one interface will be assigned the all zero subnet as it's IP and the other will be assigned the broadcast IP address for that subnet? Steve VoIP Guy wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... I know that, but the network and broadcast addresses are unusable. Thus the two good addresses for hosts. Craig Columbus wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... With a /30 you use 4 IP addresses (network, 2 node, 1 broadcast). You save addresses with a /31. Here's a link with more info: http://www.ietf.org/rfc/rfc3021.txt?number=3021 Thanks, Craig At 08:32 AM 11/30/2001 -0500, you wrote: Maybe I'm missing something, but there are only 2 useable addresses in a /30, and only 2 interfaces participating in a point-to-point link, so how are there 50% of the addresses wasted. Steve MADMAN wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... Point to point connections, with a /30 you waste 50% of the avaivalable addresses. Dave Nicolas FEVRIER wrote: Hi group, I'm puzzled by the use of /31 subnets... Anybody can explain me the benefits of such a subnet on an interface ? Thanxx. Nicolas. -- David Madland Sr. Network Engineer CCIE# 2016 Qwest Communications Int. Inc. [EMAIL PROTECTED] 612-664-3367 Emotion should reflect reason not guide it Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=27807t=27802 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: /31 subnet (now with info link) [7:27802]
It's wasn't supported until 12.2(4)T. Check it out. This is from a 1750 running 12.2(4)T: interface Loopback9 ip address 111.11.1.1 255.255.255.254 It works! -Eric -Original Message- From: VoIP Guy [mailto:[EMAIL PROTECTED]] Sent: Friday, November 30, 2001 8:34 AM To: [EMAIL PROTECTED] Subject: Re: /31 subnet (now with info link) [7:27802] Just tried it and the router dosen't even allow an interface to use a /31 mask, even with ip subnet-zero enabled. VoIP Guy wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... I read the RFC, so I guess it can be used. My bad. AM I correct in saying that one interface will be assigned the all zero subnet as it's IP and the other will be assigned the broadcast IP address for that subnet? Steve VoIP Guy wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... I know that, but the network and broadcast addresses are unusable. Thus the two good addresses for hosts. Craig Columbus wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... With a /30 you use 4 IP addresses (network, 2 node, 1 broadcast). You save addresses with a /31. Here's a link with more info: http://www.ietf.org/rfc/rfc3021.txt?number=3021 Thanks, Craig At 08:32 AM 11/30/2001 -0500, you wrote: Maybe I'm missing something, but there are only 2 useable addresses in a /30, and only 2 interfaces participating in a point-to-point link, so how are there 50% of the addresses wasted. Steve MADMAN wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... Point to point connections, with a /30 you waste 50% of the avaivalable addresses. Dave Nicolas FEVRIER wrote: Hi group, I'm puzzled by the use of /31 subnets... Anybody can explain me the benefits of such a subnet on an interface ? Thanxx. Nicolas. -- David Madland Sr. Network Engineer CCIE# 2016 Qwest Communications Int. Inc. [EMAIL PROTECTED] 612-664-3367 Emotion should reflect reason not guide it Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=27818t=27802 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: /31 subnet (now with info link) [7:27802]
I jusr dl'd that image from Cisco and it does work! I learn something new every day in thhis field. (Actually more like 10 new things everyday). Steve Lange, Eric wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... It's wasn't supported until 12.2(4)T. Check it out. This is from a 1750 running 12.2(4)T: interface Loopback9 ip address 111.11.1.1 255.255.255.254 It works! -Eric -Original Message- From: VoIP Guy [mailto:[EMAIL PROTECTED]] Sent: Friday, November 30, 2001 8:34 AM To: [EMAIL PROTECTED] Subject: Re: /31 subnet (now with info link) [7:27802] Just tried it and the router dosen't even allow an interface to use a /31 mask, even with ip subnet-zero enabled. VoIP Guy wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... I read the RFC, so I guess it can be used. My bad. AM I correct in saying that one interface will be assigned the all zero subnet as it's IP and the other will be assigned the broadcast IP address for that subnet? Steve VoIP Guy wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... I know that, but the network and broadcast addresses are unusable. Thus the two good addresses for hosts. Craig Columbus wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... With a /30 you use 4 IP addresses (network, 2 node, 1 broadcast). You save addresses with a /31. Here's a link with more info: http://www.ietf.org/rfc/rfc3021.txt?number=3021 Thanks, Craig At 08:32 AM 11/30/2001 -0500, you wrote: Maybe I'm missing something, but there are only 2 useable addresses in a /30, and only 2 interfaces participating in a point-to-point link, so how are there 50% of the addresses wasted. Steve MADMAN wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... Point to point connections, with a /30 you waste 50% of the avaivalable addresses. Dave Nicolas FEVRIER wrote: Hi group, I'm puzzled by the use of /31 subnets... Anybody can explain me the benefits of such a subnet on an interface ? Thanxx. Nicolas. -- David Madland Sr. Network Engineer CCIE# 2016 Qwest Communications Int. Inc. [EMAIL PROTECTED] 612-664-3367 Emotion should reflect reason not guide it Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=27819t=27802 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: /31 subnet (now with info link) [7:27802]
I read the RFC, so I guess it can be used. My bad. AM I correct in saying that one interface will be assigned the all zero subnet as it's IP and the other will be assigned the broadcast IP address for that subnet? Steve Yes. It's a controlled violation of that addressing rule. VoIP Guy wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... I know that, but the network and broadcast addresses are unusable. Thus the two good addresses for hosts. Craig Columbus wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... With a /30 you use 4 IP addresses (network, 2 node, 1 broadcast). You save addresses with a /31. Here's a link with more info: http://www.ietf.org/rfc/rfc3021.txt?number=3021 Thanks, Craig At 08:32 AM 11/30/2001 -0500, you wrote: Maybe I'm missing something, but there are only 2 useable addresses in a /30, and only 2 interfaces participating in a point-to-point link, so how are there 50% of the addresses wasted. Steve MADMAN wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... Point to point connections, with a /30 you waste 50% of the avaivalable addresses. Dave Nicolas FEVRIER wrote: Hi group, I'm puzzled by the use of /31 subnets... Anybody can explain me the benefits of such a subnet on an interface ? Thanxx. Nicolas. -- David Madland Sr. Network Engineer CCIE# 2016 Qwest Communications Int. Inc. [EMAIL PROTECTED] 612-664-3367 Emotion should reflect reason not guide it Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=27823t=27802 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Subject: Re: /31 subnet (now with info link) [7:27802]
I would like to amplify Howard's comments below and doubly
stress two words in his one line explanation,
namely controlled and violation.
In terms of **Internet Gateways** (read routers) this is an
acceptable practice for what the RFC describes in its
title, Using 31-Bit Prefixes on IPv4 Point-to-Point Links.
In my humble opinion, that is the **ONLY** place where this
should be used. A case in point is this:
3.1. Requirements for Internet Hosts -- Communication Layers
[RFC1122]
Section 3.2.1.3 (e) is replaced with:
(e) { , , -1 }
Directed broadcast to the specified subnet. It MUST
NOT be used as a source address, except when the originator is
one of the endpoints of a point-to-point link with a 31-bit
mask.
Anybody want to take any bets as to how well that will work on
your standard Winthing? I already tried it, and it is very
unhappy (to put it mildly). This goes back to a previous post
and a previous discussion we had about IP subnet zero and the
subtle differences spelled out on RFC 1122 and RFC 1812. I
submit then, as I do now, that RFC 1122 does still remain in
force and describe the intended behavior of Internet hosts (non-
Gateways/routers). Personally, I would not have recommended
the change listed in the paragraph above, since it clearly has
very little relevance (how many Internet hosts sit on a local
area network with a point to point connection?)
If what I said was not clear enough, heed these words - test
this out wherever you think you may want to implement it, and
make sure it works for everything you need to do.
I can't wait to shed the legacy baggage of IPv4.
v/r,
Paul Werner
I read the RFC, so I guess it can be used. My bad.
AM I correct in saying that one interface will be assigned
the all zero
subnet as it's IP and the other will be assigned the
broadcast IP
address
for that subnet?
Steve
Yes. It's a controlled violation of that addressing rule.
Get your own 800 number
Voicemail, fax, email, and a lot more
http://www.ureach.com/reg/tag
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7i=27878t=27802
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Re: /31 subnet (now with info link) [7:27802]
Lange, Eric wrote: It's wasn't supported until 12.2(4)T. Check it out. This is from a 1750 running 12.2(4)T: interface Loopback9 ip address 111.11.1.1 255.255.255.254 It works! For a loopback, so does a /32 :-) Jeff Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=27905t=27802 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
