From: Jeff Omick (jomick@xxxxxxxxxx)
Date: Tue Aug 07 2001 - 23:27:26 GMT-3
Here is an excerpt from rfc 1918.
3 Private Address Space
The Internet Assigned Numbers Authority (IANA) has reserved the following
three blocks of the
IP address space for private internets:
10.0.0.0 - 10.255.255.255 (10/8 prefix)
172.16.0.0 - 172.31.255.255 (172.16/12 prefix)
192.168.0.0 - 192.168.255.255 (192.168/16 prefix)
Jeff Omick
Andrew Lennon wrote:
>
> Monty,
>
> 192.168.0.0 can be a /8 (not recommended though). You need to think
> CIDR. Because the address range starts at 192.0.0.0 and ends at
> 192.255.255.255, any address within that range is valid (no rfc 1918's
> though). Hence if you are a crap ISP you can aggregate incorrectly and
> advertise Martian Networks. Once this has happened, it is up to the
> upstream ISP to block these using route-maps/communities etc.
>
> Same applies to, say, 172.23.1.1/24. this should be filtered by the
> upstream ISP
>
> Using BGP aggregation with summary suppression and/or communities would
> allow you to advertise those routes that are valid within the 192/8
> block and shut out those not valid.
>
> Providing you are not connecting to an address (rfc 1918) in that range
> from a globally routable address and not passing though an intermediary
> trying to route the same range you should be fine.
>
> There are other addresses within the 192/8 block on top of those
> specified in rfc 1918 which are not routable, but I can't remember now!
>
> So far I know of the following:
>
> 10/8
> 66.0.0.0 - 126.0.0.0
> 164.0.0.0 -191.255.255.255 (some are in use now I think. 165-170 maybe)
>
> Anyone know of any others outside this, let me know!
>
> Andy
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Monty.Majszak@Level3.com
> Sent: 07 August 2001 19:31
> To: austin.alao@bt.com; andrew.2.shore@bt.com; Leonard_Ong@iname.com;
> ccielab@groupstudy.com
> Subject: RE: Routing
>
> I must be missing something here Austin?! 192.168.0.0 cannot be a /8.
> Technically the network address would be just 192.0.0.0 but the
> "private"
> address space of 192.168.0.0 falls w/in that block. Let me know if I
> missed
> something here or misunderstood you, thanks.
>
> -Monty
>
> "The point is that f you look carefully at the RFC, it specifies the
> address
> AND mask. Any bit shifting that alters the network prefix position
> towards
> the most significant direction, will render the route routable.
>
> 192.168.x.x is Internet routable when the mask is 255.0.0.0 that is the
> whole thinking behind CDR. Makes hitherto illegal addresses useable in a
> way."
>
> -----Original Message-----
> From: austin.alao@bt.com [mailto:austin.alao@bt.com]
> Sent: Tuesday, August 07, 2001 9:23 AM
> To: andrew.2.shore@bt.com; Leonard_Ong@iname.com; ccielab@groupstudy.com
> Subject: RE: Routing
>
> Thought I had answered the question 2 hours ago only to find out I
> forgot
> to click "send".
>
> Anyhow here goes again:
>
> When dealing with protocols like BGP and OSPF an address means nothing
> without its mask.
>
> With CIDR which you are seeing in action here, 172.16.3.1 is not
> routable
> when the mask is /16. Move it to anything less and it is a valid
> Internet
> address.
>
> The point is that f you look carefully at the RFC, it specifies the
> address
> AND mask. Any bit shifting that alters the network prefix position
> towards
> the most significant direction, will render the route routable.
>
> 192.168.x.x is Internet routable when the mask is 255.0.0.0 that is the
> whole thinking behind CDR. Makes hitherto illegal addresses useable in a
> way.
>
> Trace and ping are limited network routing testing tools. And are more
> suitable and yet nor perfect for reachability testing for this exact
> reason
> that you cannot specify a prefix length.
>
> Until we now what the masks are on those routers we cannot tell if the
> address space is routable or not.
>
> 172.x.x.x /8 s a valid Internet address.
>
> Believe me people the first email was more elegant than this.
>
> Cheers
>
> Austin Alao,
> 01442 431 247 / 07764 356 424
> "The significant problems we face cannot be solved at the same level of
> thinking we were at when we created them."
> -Albert Einstein.
>
> -----Original Message-----
> From: Shore,A,Andrew,IWO SHOREA2 C
> Sent: 06 August 2001 07:46
> To: Leonard_Ong@iname.com; ccielab@groupstudy.com
> Subject: RE: Routing
>
> In many data centres ISPs use privately addressed transit networks which
> are
> not publicly accessible unless you are going through it i.e.
>
> R1- 201.234.93.3 ----> R2 156.3.6.77 ----> R3 172.16.3.1 ----> R4
> 76.4.56.3
> www ISP outside int ISP internal net ISP
> public
> server network
>
> The 172 network is only used internally to the data centre.
>
> Try tracing to the 172 network and you can't ! as routes to it are only
> know
> by R2
>
> hope this makes sense.
>
> Andrew Shore. CCNP+Security, MCSE, CCP, BSc
> Network Consultant
> Internetworking Solutions Limited
>
> -----Original Message-----
> From: Leonard @ iname.com [mailto:Leonard_Ong@iname.com]
> Sent: 06 August 2001 14:20
> To: ccielab@groupstudy.com
> Subject: Routing
>
> Hello Guys,
>
> I found some traceroute that really bothers me and I don't know the
> answer. Would you kindly explain it to me ?
>
> traceroute from access.net.id to 202.156.227.140
>
> 1 202.180.0.4 (202.180.0.4) 2.502 ms 2.017 ms 1.641 ms
> 2 202.155.7.25 (202.155.7.25) 91.019 ms 28.084 ms 30.019 ms
> 3 202.155.7.85 (202.155.7.85) 55.545 ms 59.557 ms 23.195 ms
> 4 202.155.7.246 (202.155.7.246) 62.904 ms 25.812 ms 68.068 ms
> 5 500.POS1-2.IG2.SAC1.ALTER.NET (157.130.193.221) 210.419 ms
> 210.405
> ms 305.777 ms
> 6 0.so-0-0-0.XR2.SAC1.ALTER.NET (152.63.54.118) 240.747 ms 208.259
> ms 216.579 ms
> 7 0.so-0-0-0.TR2.SAC1.ALTER.NET (152.63.3.197) 247.044 ms 217.252
> ms 253.461 ms
> 8 127.ATM5-0.IR2.SAC1.ALTER.NET (152.63.11.113) 209.069 ms 226.315
> ms 208.555 ms
> 9 POS3-0.IR2.SAC2.ALTER.NET (137.39.31.209) 204.193 ms 209.688
> ms 265.266 ms
> 10 210.80.49.230 (210.80.49.230) 441.732 ms
> 335.ATM5-0-0.TR2.SIN1.ALTER.NET (210.80.51.142) 514.855 ms
> 435.ATM5-0-0.TR2.SIN1.ALTER.NET (210.80.51.134) 526.292 ms
> 11 POS1-0-0.XR2.SIN1.Alter.Net (210.80.48.62) 456.046 ms 473.853
> ms 472.113 ms
> 12 312.ATM3-0-0.GW2.SIN1.Alter.Net (210.80.2.202) 451.268 ms 458.89
> ms 434.287 ms
> 13 scv-gw-33.customer.alter.net (202.95.97.14) 544.822 ms 450.079
> ms 460.404 ms
> 14 172.20.6.11 (172.20.6.11) 466.566 ms 516.396 ms 464.313 ms
> 15 172.20.2.15 (172.20.2.15) 458.438 ms 464.12 ms 446.679 ms
> 16 172.20.15.2 (172.20.15.2) 465.278 ms 476.811 ms 570.675 ms
> 17 mcns140.docsis227.singa.pore.net (202.156.227.140) 493.695 ms
> 494.196
> ms 525.214 ms
>
> If you check the entry 14-16 it is private address which is supposedly
> not
> routeable... and it goes at entry 17 to end-host of this ISP/cable...
> which
> is routeable address... Any idea ?
>
> Thanks
> **Please read:http://www.groupstudy.com/list/posting.html
> **Please read:http://www.groupstudy.com/list/posting.html
> **Please read:http://www.groupstudy.com/list/posting.html
> **Please read:http://www.groupstudy.com/list/posting.html
This archive was generated by hypermail 2.1.4 : Thu Jun 13 2002 - 10:31:46 GMT-3