Top Document: comp.dcom.sys.cisco Frequently Asked Questions (FAQ) Previous Document: What are some methods for conserving IP addresses for serial lines? Next Document: How do 4xxx serial numbers correspond to models? See reader questions & answers on this topic! - Help others by sharing your knowledge How come my cisco router doesn't accept an address like: "ip address 192.111.107.1 255.255.255.240" or "ip address 171.69.0.1 255.255.0.0" When "subnetting" of IP networks was first sanctioned by the IETF, the first and last subnets (the all zeros subnet and all ones subnet) were reserved for rather obscure uses and because of the confusion that would be caused with routing protocols that don't carry net mask information. It was technically illegal to place hosts or routers on those two subnets. Several hosts and most other vendor's router products have problems operating with the reserved subnets, so their use is discouraged. However, in 1995, the IETF removed the restrictions on the use of these reserved subnets as part of the classless routing effort. If you would like to use the reserved subnets, simply add the line "ip subnet-zero" to your cisco configuration. You might consider adding "ip subnet-zero" to all your configurations as a metter of course, to avoid being bitten by this in the future. User Contributions:Top Document: comp.dcom.sys.cisco Frequently Asked Questions (FAQ) Previous Document: What are some methods for conserving IP addresses for serial lines? Next Document: How do 4xxx serial numbers correspond to models? Single Page [ Usenet FAQs | Web FAQs | Documents | RFC Index ] Send corrections/additions to the FAQ Maintainer: cisco-faq@panix.com (comp.dcom.sys.cisco FAQ responses)
Last Update March 27 2014 @ 02:11 PM
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