Re: Inverse Mask
It represents the netmask (255.248.0.0) for the network. The easiest way to get from an inverse mask to a regular netmask is like this: 255.255.255.255 fill 'er up - 000.007.255.255 subtract the inverse mask --- 255.248.000.000 real netmask So, if you have a 0.7.255.255 inverse mask, it equates to 255.248.0.0. Likewise, if you had 0.0.15.255, the mask would be 255.255.240.0. You can also take the normal mask and get the inverse mask by doing the opposite. 255.255.255.255 - 255.248.000.000 --- 000.007.255.255 -j On Tue, 24 Oct 2000, Keith Townsend wrote: I need help in understanding inverse masks that are used in network access list commands. I understabd what 0 and 255 do but I get confused when there is any number other than these two. For example... network 10.0.0.0 0.7.255.255 area 0 what does the 7 represent or specifiy for the mask. Thanks Keith _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Inverse Mask
take 255.255.255.255 and subtract your reverse mask to get actual mask EX 255.255.255.255 - 0. 7.255.255 255.248. 0. 0 -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Keith Townsend Sent: Tuesday, October 24, 2000 12:15 PM To: [EMAIL PROTECTED] Subject: Inverse Mask I need help in understanding inverse masks that are used in network access list commands. I understabd what 0 and 255 do but I get confused when there is any number other than these two. For example... network 10.0.0.0 0.7.255.255 area 0 what does the 7 represent or specifiy for the mask. Thanks Keith _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Inverse Mask
thanks j never thought of it that way used to do it the long way Duck - Original Message - From: J Rowley [EMAIL PROTECTED] To: Keith Townsend [EMAIL PROTECTED] Cc: [EMAIL PROTECTED] Sent: Tuesday, October 24, 2000 10:44 AM Subject: Re: Inverse Mask It represents the netmask (255.248.0.0) for the network. The easiest way to get from an inverse mask to a regular netmask is like this: 255.255.255.255 fill 'er up - 000.007.255.255 subtract the inverse mask --- 255.248.000.000 real netmask So, if you have a 0.7.255.255 inverse mask, it equates to 255.248.0.0. Likewise, if you had 0.0.15.255, the mask would be 255.255.240.0. You can also take the normal mask and get the inverse mask by doing the opposite. 255.255.255.255 - 255.248.000.000 --- 000.007.255.255 -j On Tue, 24 Oct 2000, Keith Townsend wrote: I need help in understanding inverse masks that are used in network access list commands. I understabd what 0 and 255 do but I get confused when there is any number other than these two. For example... network 10.0.0.0 0.7.255.255 area 0 what does the 7 represent or specifiy for the mask. Thanks Keith _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Inverse Mask
Do you know any shortcut to solve this kind of problem: Implement an access list to block the odd numbers of 255.248.0.0 Thanks, Billy ""Donald B Johnson Jr"" [EMAIL PROTECTED] wrote in message 018a01c03e11$a659e810$[EMAIL PROTECTED]">news:018a01c03e11$a659e810$[EMAIL PROTECTED]... thanks j never thought of it that way used to do it the long way Duck - Original Message - From: J Rowley [EMAIL PROTECTED] To: Keith Townsend [EMAIL PROTECTED] Cc: [EMAIL PROTECTED] Sent: Tuesday, October 24, 2000 10:44 AM Subject: Re: Inverse Mask It represents the netmask (255.248.0.0) for the network. The easiest way to get from an inverse mask to a regular netmask is like this: 255.255.255.255 fill 'er up - 000.007.255.255 subtract the inverse mask --- 255.248.000.000 real netmask So, if you have a 0.7.255.255 inverse mask, it equates to 255.248.0.0. Likewise, if you had 0.0.15.255, the mask would be 255.255.240.0. You can also take the normal mask and get the inverse mask by doing the opposite. 255.255.255.255 - 255.248.000.000 --- 000.007.255.255 -j On Tue, 24 Oct 2000, Keith Townsend wrote: I need help in understanding inverse masks that are used in network access list commands. I understabd what 0 and 255 do but I get confused when there is any number other than these two. For example... network 10.0.0.0 0.7.255.255 area 0 what does the 7 represent or specifiy for the mask. Thanks Keith _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Inverse Mask
Sorry. Let me correct this: Implement an access-list to block only the odd numbers (4th octet) of 123.12.10.x Thanks, Billy ""Billy Monroe"" [EMAIL PROTECTED] wrote in message 8t52r7$2g9$[EMAIL PROTECTED]">news:8t52r7$2g9$[EMAIL PROTECTED]... Do you know any shortcut to solve this kind of problem: Implement an access list to block the odd numbers of 255.248.0.0 Thanks, Billy ""Donald B Johnson Jr"" [EMAIL PROTECTED] wrote in message 018a01c03e11$a659e810$[EMAIL PROTECTED]">news:018a01c03e11$a659e810$[EMAIL PROTECTED]... thanks j never thought of it that way used to do it the long way Duck - Original Message - From: J Rowley [EMAIL PROTECTED] To: Keith Townsend [EMAIL PROTECTED] Cc: [EMAIL PROTECTED] Sent: Tuesday, October 24, 2000 10:44 AM Subject: Re: Inverse Mask It represents the netmask (255.248.0.0) for the network. The easiest way to get from an inverse mask to a regular netmask is like this: 255.255.255.255 fill 'er up - 000.007.255.255 subtract the inverse mask --- 255.248.000.000 real netmask So, if you have a 0.7.255.255 inverse mask, it equates to 255.248.0.0. Likewise, if you had 0.0.15.255, the mask would be 255.255.240.0. You can also take the normal mask and get the inverse mask by doing the opposite. 255.255.255.255 - 255.248.000.000 --- 000.007.255.255 -j On Tue, 24 Oct 2000, Keith Townsend wrote: I need help in understanding inverse masks that are used in network access list commands. I understabd what 0 and 255 do but I get confused when there is any number other than these two. For example... network 10.0.0.0 0.7.255.255 area 0 what does the 7 represent or specifiy for the mask. Thanks Keith _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Inverse Mask
have a look at: - http://www.cursos.telemidia.puc-rio.br/cursos_cce/cursotcp/CIDR-FAQ.HTM - http://www.learntosubnet.com/ - http://www.3com.com/nsc/501302s.html - www.itprc.com/tcp_ip.htm In your below example, the "7" is an inverse mask for 248. (255-7=248) Irwin -Original Message- From: Keith Townsend [mailto:[EMAIL PROTECTED]] Sent: Tuesday, October 24, 2000 12:15 PM To: [EMAIL PROTECTED] Subject: Inverse Mask I need help in understanding inverse masks that are used in network access list commands. I understabd what 0 and 255 do but I get confused when there is any number other than these two. For example... network 10.0.0.0 0.7.255.255 area 0 what does the 7 represent or specifiy for the mask. Thanks Keith _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Inverse Mask
Here's the math.. 255.255.255.255 -mask you'd expect --- inverse mask so, the 0.7.255.255 inverse mask is what you'd typically see as a 255.248.0.0 subnet Brian On Tue, 24 Oct 2000, Keith Townsend wrote: I need help in understanding inverse masks that are used in network access list commands. I understabd what 0 and 255 do but I get confused when there is any number other than these two. For example... network 10.0.0.0 0.7.255.255 area 0 what does the 7 represent or specifiy for the mask. Thanks Keith _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Inverse Mask
Hmm, the only way I know how to do that is to write a shell script and then copy and paste the output into an access-list. #!/bin/sh i=1 echo "access-list 1 deny 123.12.10.$i" while [ $i -lt 255 ] do i=`expr $i + 2` echo "access-list 1 deny 123.12.10.$i" done [j][www][22:24:25][~]$ sh foo access-list 1 deny 123.12.10.1 access-list 1 deny 123.12.10.3 access-list 1 deny 123.12.10.5 access-list 1 deny 123.12.10.7 ... [snip] -j :) - Original Message - From: "Billy Monroe" [EMAIL PROTECTED] Newsgroups: groupstudy.cisco To: [EMAIL PROTECTED] Sent: Tuesday, October 24, 2000 6:34 PM Subject: Re: Inverse Mask Sorry. Let me correct this: Implement an access-list to block only the odd numbers (4th octet) of 123.12.10.x Thanks, Billy ""Billy Monroe"" [EMAIL PROTECTED] wrote in message 8t52r7$2g9$[EMAIL PROTECTED]">news:8t52r7$2g9$[EMAIL PROTECTED]... Do you know any shortcut to solve this kind of problem: Implement an access list to block the odd numbers of 255.248.0.0 Thanks, Billy ""Donald B Johnson Jr"" [EMAIL PROTECTED] wrote in message 018a01c03e11$a659e810$[EMAIL PROTECTED]">news:018a01c03e11$a659e810$[EMAIL PROTECTED]... thanks j never thought of it that way used to do it the long way Duck - Original Message - From: J Rowley [EMAIL PROTECTED] To: Keith Townsend [EMAIL PROTECTED] Cc: [EMAIL PROTECTED] Sent: Tuesday, October 24, 2000 10:44 AM Subject: Re: Inverse Mask It represents the netmask (255.248.0.0) for the network. The easiest way to get from an inverse mask to a regular netmask is like this: 255.255.255.255 fill 'er up - 000.007.255.255 subtract the inverse mask --- 255.248.000.000 real netmask So, if you have a 0.7.255.255 inverse mask, it equates to 255.248.0.0. Likewise, if you had 0.0.15.255, the mask would be 255.255.240.0. You can also take the normal mask and get the inverse mask by doing the opposite. 255.255.255.255 - 255.248.000.000 --- 000.007.255.255 -j On Tue, 24 Oct 2000, Keith Townsend wrote: I need help in understanding inverse masks that are used in network access list commands. I understabd what 0 and 255 do but I get confused when there is any number other than these two. For example... network 10.0.0.0 0.7.255.255 area 0 what does the 7 represent or specifiy for the mask. Thanks Keith _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Inverse Mask
0.7.255.255 is like .0111.. In that case, your mask starts where the 1's start. MGR Keith Townsend wrote: I need help in understanding inverse masks that are used in network access list commands. I understabd what 0 and 255 do but I get confused when there is any number other than these two. For example... network 10.0.0.0 0.7.255.255 area 0 what does the 7 represent or specifiy for the mask. Thanks Keith _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Inverse Mask
Inverse masks are loopy. Just think the opposite a subnet maks. Instead of contiguous bit from left to right these are contiguous bits right to left. wildcard masks and inverse masks are different. I don't think you use inverse masks for EIGRP or IGRP though as you have that network statement. "network 10.0.0.0 0.7.255.255 area 0" Brian From: "Keith Townsend" [EMAIL PROTECTED] Reply-To: "Keith Townsend" [EMAIL PROTECTED] To: [EMAIL PROTECTED] Subject: Inverse Mask Date: Tue, 24 Oct 2000 11:15:10 -0500 I need help in understanding inverse masks that are used in network access list commands. I understabd what 0 and 255 do but I get confused when there is any number other than these two. For example... network 10.0.0.0 0.7.255.255 area 0 what does the 7 represent or specifiy for the mask. Thanks Keith _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. Share information about yourself, create your own public profile at http://profiles.msn.com. _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Inverse Mask
Remember that with ACL masks, 1s = don't care. so, for a mask of 0.7.255.255 you have - .0111.. so, when used with 10.0.0.0 - You have to have 10 in the first octet (no ones) It doesn't care what is in the 3rd and 4th octet (all ones) The second octet is the one to watch. because the mask is 0111 the first five bits have to remain as they are in the ip address - 0 the last three bits can be either one or zero, doesn't matter so, they can be anything from 000 to 111 so, your IP address can be 0 000 to 0 111 which gives you 0 - 7 in decimal so the mask fits 10.0.0.0 to 10.7.255.255 hope that helps Mike I need help in understanding inverse masks that are used in network access list commands. I understabd what 0 and 255 do but I get confused when there is any number other than these two. For example... network 10.0.0.0 0.7.255.255 area 0 what does the 7 represent or specifiy for the mask. Thanks Keith _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. Share information about yourself, create your own public profile at http://profiles.msn.com. _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Inverse Mask
How 'bout: deny 123.12.10.1 0.0.0.254 permit any ---JRE--- ""Billy Monroe"" [EMAIL PROTECTED] wrote in message 8t532p$2vv$[EMAIL PROTECTED]">news:8t532p$2vv$[EMAIL PROTECTED]... Sorry. Let me correct this: Implement an access-list to block only the odd numbers (4th octet) of 123.12.10.x Thanks, Billy ""Billy Monroe"" [EMAIL PROTECTED] wrote in message 8t52r7$2g9$[EMAIL PROTECTED]">news:8t52r7$2g9$[EMAIL PROTECTED]... Do you know any shortcut to solve this kind of problem: Implement an access list to block the odd numbers of 255.248.0.0 Thanks, Billy ""Donald B Johnson Jr"" [EMAIL PROTECTED] wrote in message 018a01c03e11$a659e810$[EMAIL PROTECTED]">news:018a01c03e11$a659e810$[EMAIL PROTECTED]... thanks j never thought of it that way used to do it the long way Duck - Original Message - From: J Rowley [EMAIL PROTECTED] To: Keith Townsend [EMAIL PROTECTED] Cc: [EMAIL PROTECTED] Sent: Tuesday, October 24, 2000 10:44 AM Subject: Re: Inverse Mask It represents the netmask (255.248.0.0) for the network. The easiest way to get from an inverse mask to a regular netmask is like this: 255.255.255.255 fill 'er up - 000.007.255.255 subtract the inverse mask --- 255.248.000.000 real netmask So, if you have a 0.7.255.255 inverse mask, it equates to 255.248.0.0. Likewise, if you had 0.0.15.255, the mask would be 255.255.240.0. You can also take the normal mask and get the inverse mask by doing the opposite. 255.255.255.255 - 255.248.000.000 --- 000.007.255.255 -j On Tue, 24 Oct 2000, Keith Townsend wrote: I need help in understanding inverse masks that are used in network access list commands. I understabd what 0 and 255 do but I get confused when there is any number other than these two. For example... network 10.0.0.0 0.7.255.255 area 0 what does the 7 represent or specifiy for the mask. Thanks Keith _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Inverse Mask
Hi Keith, What I find helpful is to do this for inverse masks: Just subtract the number from 255. So for your 7, it will be 255-7 which is 248. Hope that helps Helena On Tue, 24 Oct 2000, Keith Townsend wrote: I need help in understanding inverse masks that are used in network access list commands. I understabd what 0 and 255 do but I get confused when there is any number other than these two. For example... network 10.0.0.0 0.7.255.255 area 0 what does the 7 represent or specifiy for the mask. Thanks Keith _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
