IP Addressing Query

What does the following IP addressing mean:

81.xxx.xxx.xxx/29
WAN 81.nnn.nnn.nnn

Where a TBB Speedtest returns the IP address 81.xxx.xxx.6

I'm confused Give me a soldering iron any day...

Edited to add: nnn are different to xxx

Cheers!

Edited by Ancient_Mariner (Sat 22-Jan-22 15:04:39)

Who is your ISP, and where did you get the first two lines form?

In reply to a post by Ancient_Mariner:

What does the following IP addressing mean:
81.xxx.xxx.xxx/29
WAN 81.nnn.nnn.nnn

/29 is the CIDR notation for the number of bit set in the mask. /29 means a subnet mask of 255.255.255.248, which means the IP addresses from 81.x.x.1 to 81.x.x.6 are usable by your network.

The WAN IP quoted is the address you should assign to your router on the public interface that faces the ISP, typically that using PPPoE, IPoA or DHCP depending on your ISP.

I'm confused Give me a soldering iron any day...
Edited to add: nnn are different to xxx

They will be as one is the ISP network, and one is the IP network they are assigning to you. This is only required where you have more then ONE public IP from the ISP. The majority of domestic ISPs only support a single IP so the home user has no choice but to translate that IP to a private (RFC 1918) network inside the premises.

However some ISPs will sell you a range of addresses (for money) and then this information is supplied.

In reply to a post by Michael_Chare:

Who is your ISP, and where did you get the first two lines form?

Signature says AAISP whom often provide blocks of routable IPv4 and whole networks of IPv6 to their customers. Unlike the mass market ISPs of Virgin Media, BT Retail, TalkTalk, Sky, whom only supply a single IPv4 for the router/gateway itself.

In reply to a post by jchamier:

The WAN IP quoted is the address you should assign to your router on the public interface that faces the ISP, typically that using PPPoE, IPoA or DHCP depending on your ISP.

More likely to be IPoE than IPoA.

I don't think ATM is used much if at all, apart from on ADSL. Even then it's only the ADSL part of the circuit that uses ATM. The fixed 53 byte packets on ATM makes it a poor choice for carrying traffic.

A&A as per my sig.

My control panel gives those two lines. Normally when I do, say a TBB Speedtest I see the
81.nnn.nnn.nnn IP address.

However to aid a check into dropouts, A&A have sent me a loan router; normally I use my own DrayTek. Using the loan router, a TBB Speedtest shows 81.xxx.xxx.6 and not the usual 81.nnn.nnn.nnn IP Address.

Cheers!

As in my reply to Michael above, my control panel gives those two lines. Normally when I do, say a TBB Speedtest I see the 81.nnn.nnn.nnn IP address.

However to aid a check into dropouts, A&A have sent me a loan router; normally I use my own DrayTek. Using the loan router, a TBB Speedtest shows 81.xxx.xxx.6 and not the usual 81.nnn.nnn.nnn IP Address.

Does that suggest that with the 81.xxx.xxx.6 address being visible on a TBB Speedtest, that it has "escaped" from just being an address for my network?

Currently I cannot access the loan router's control panel.

Cheers!

As already answered, the xxx addresses are from your real allocated public IP subnet (a pool of up to 6* usable addresses).
The xxx address is correctly shown as the source of the traffic in the test.
It's not leakage (because it's already a public routable address and does not need NATting again).

The nnn address is merely the IP the router is using to route traffic to/from the ISP. It's not the source of the traffic.
When you have a routed subnet, you should think of that as being part of the first hop but just happens to be physically on premises.

I realise people find it counter-intuitive because they are so used to having only one address and think the WAN interface of the router being the only place where a public IPs should exist.

Even when you have a routed public subnet, you can still use private addressing within your network, it's just that you then have more then 1 real public IP available to NAT those to on the way out.

When you have been using your own Draytek, you haven't actually been making use of your allocated public IP range.

(*) Technically the router will use up 1 of those addresses to be the gateway for the rest of that subnet so you will have 5 public addresses left to assign either directly to specific services or for NAT mappings.

0 = network number (prefix address seen in the CIDR notation as prefix/size; for example /29 this will be 0, or any other multiple of 8 up to 248 and what follows will be relative to that)
+1 = router as gateway
+2 - 6 usable
+7 = broadcast

Edited by prlzx (Sun 23-Jan-22 01:41:14)

I suspect that, despite having a public /29 you have your own router set to NAT

A&A use PPPoE, so the PPP endpoint has it's own IP address which is in addition to your /29 range of addresses - mine is 81.187.nnn.nn7, yours will be the 81.nnn.nnn.nnn address that you mentioned.

As well as that you have your /29 - as others have said this gives 29 bits of network address and 3 bits of host address. The hosts with all bits zero and all bits one have special meanings (network and broadcast) so you have 6 routeable addresses - as you mentioned 81.xxx.xxx.6 being one of them you will have 81.xxx.xxx.1 through to 81.xxx.xxx.6

As you have NAT set on your router anytime you access the 'net - eg to do a speed test the other end will see the IP address associated with your PPP connection.

The loan router from A&A is clearly set up to not apply NAT - to be honest this is the correct way to do it if your 6 addresses covers all of your needs. this is why the "other end" is now seeing the actual address of the PC (or whatever) you are using.

In this case I would disable NAT - it is not doing anything useful, in particular it does not protect your hosts from rogue packets - anyone on the internet can send a packet to 81.xxx.xxx.6, Andrews and Arnold will send it down the PPP link for you and, unless it is firewalled, your router will forward it onto the local network. Your firewall settings are your protection, not NAT

Thanks for all the responses.

Like I said in my OP, give me a soldering iron any day....

I problem I have is terminology.

I have a /29 which despite the excellent replies still has me puzzled. It seems that a /29 gives me 6 addresses. But is 6 enough? At times I have 3 pcs, an iPad, 2 printers, a wi-fi access point, a smart phone plus a wireless hub for our EV charger, a couple of networked pieces of radio equipment and 3 TVs plus a TV dongle. Heck, that's more than I expected, but the DHCP list on the DrayTek seems to agree it. Now they all work OK with NAT so I am sure that they could with the /29 but how do I configure it all?

Is there a recommended guide for setting up home networks which covers this, or is it that a /29 suggests an office network and a network professional is required? Rather like buying a car, the handbook tells you what is where, but not necessarily how and when to use it, let alone how to drive.

Cheers!