sub-interfaces are for fast-ethernet interfaces configured for VLANs (one physical interface, many logical or virtual).
If possible, you should avoid secondary addressing. I have seen networks with up to 5 IP segments running on a single Ethernet interface (4 secondary addresses). In my experience, performance is degraded with this type of configuration. You should also note that if you're intending on using DHCP on the secondary address segment you will see that only the primary addressed segment will work. Let's take my previous example: interface ethernet 0 ip address 10.1.1.1 255.255.255.0 ip address 10.1.2.1 255.255.255.0 secondary The address the router (relay agent) puts in the DHCPDISCOVER giaddr field is the PRIMARY address (in this case 10.1.1.1). The DHCP server will use this to determine which scope (if any) to use in offering an ip address in the DHCPOFFER message back to the client, so in this case it will use 10.1.1.0. A secondary address such as the 10.1.2.1 in the above configuration will not be used. This means that you can configure the scope for the secondary address range on the DHCP server but it will NOT be used until 10.10.5.1 is configured as a primary. HTH Darren P.S. According to Cisco, you can define an unlimited number of secondary addresses. Don't believe everything you read. 8^) Check the following URL: (http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/ip_ c/ipcprt1/1cdipadr.htm#xtocid221563 ) Watch the rap. At 12:13 PM 12/27/2001 -0800, John Mairs wrote: >Thank you sir! I appreciate your time on this. one >side though if it's ok, what is the difference between >secondary interfaces and sub-interfaces? > >John > > >--- Darren Crawford wrote: >> You will have to use secondary addressing. >> >> interface ethernet 0 >> ip address 10.1.1.1 255.255.255.0 >> ip address 10.1.2.1 255.255.255.0 secondary >> >> HTH >> >> Darren >> >> At 03:10 PM 12/27/2001 -0500, John Mairs wrote: >> >Hi, >> > >> >I have a 2501 (one ethernet interface) and I wanted >> to >> >route over that interface by setting up two >> >sub-interfaces. I can't assign an address because >> it >> >replies with >> > >> >"configuring IP routing on a LLAN subinterface is >> only >> >allowed if that subinterface is already configured >> as >> >part of an IEEE 802.10 or ISL vLAN." >> > >> >what will I need to do (specifically if you can) to >> >route over a single E0 interface? >> > >> >thanks >> > >> >__________________________________________________ >> >Do You Yahoo!? >> >Send your FREE holiday greetings online! >> >http://greetings.yahoo.com >> [EMAIL PROTECTED] >> >> >> x$:0`0:$x,,,,x$:0`0:$x,,,,x$:0`0:$x,,,,x$: >> >> Lucent Technologies >> NetworkCare Professional Services >> http//www.lucent.com/netcare/ >> Darren S. Crawford - CCNP, CCDP, CCIE TBA >> >> Northwest Region - Sacramento Office >> Voicemail (916) 859-5200 x310 >> Pager (800) 467-1467 >> mailto:[EMAIL PROTECTED] >> >> x$:0`0:$x,,,,x$:0`0:$x,,,,x$:0`0:$x,,,,x$: >> >> "You always have time for things you put first" - >> Tucker Resources >> >> > > >===== >John L. Mairs > >__________________________________________________ >Do You Yahoo!? >Send your FREE holiday greetings online! >http://greetings.yahoo.com x$:0`0:$x,,,,x$:0`0:$x,,,,x$:0`0:$x,,,,x$: Lucent Technologies NetworkCare Professional Services http//www.lucent.com/netcare/ Darren S. Crawford - CCNP, CCDP, CCIE TBA Northwest Region - Sacramento Office Voicemail (916) 859-5200 x310 Pager (800) 467-1467 mailto:[EMAIL PROTECTED] x$:0`0:$x,,,,x$:0`0:$x,,,,x$:0`0:$x,,,,x$: "You always have time for things you put first" - Tucker Resources Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=30321&t=30225 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
