[j-nsp] cgnat on service module - interesting bgp advertisements

[Alexander Arseniev]

Hello,
When using "address X.Y.Z.W/TV" definition, the net and bcast IPs are 
NOT used and JUNOS carves them out.
When using "address-range low X.Y.Z.W high X.Y.W.U", ALL addresses are 
used and JUNOS does NOT carve the net and bcast IPs out.
Whether You _should_ use net and bcast IPs - it depends on the app mix.
Some legacy apps such as eMule frown upon IPs ending with 0 (i.e. net IP 
for /24), and gives them "low id"
https://en.wikipedia.org/wiki/EMule#Low_ID
HTH
Thanks
Alex

On 20/04/2016 17:11, Aaron wrote:
>
> Awesome Alex, good find !
>
> So I wonder if the high-cpu issue with the all-zero and all-ones 
> address of the named subnet means that when using address-range that 
> the net-id and bcast address for the low/high definition will NOT be 
> used in the nat pool ?  …or that net-id and bcast addresses WILL be 
> used for nat translations ?
>
> Thanks again
>
> agould at eng-lab-mx104-cgn# show | compare
>
> [edit services nat pool nat1]
>
> - address 1.2.3.128/25;
>
> [edit services nat pool nat1]
>
> + address-range low 1.2.3.128 high 1.2.3.255;
>
> agould at eng-lab-mx104-cgn# run show route advertising-protocol bgp 
> 10.101.0.2 table one.inet.0
>
> one.inet.0: 771 destinations, 1915 routes (771 active, 0 holddown, 0 
> hidden)
>
> Prefix                  Nexthop              MED Lclpref    AS path
>
> * 10.144.2.4/30           Self 100        I
>
> * 1.2.3.128/25         Self                         100 I
>
> [edit]
>
> *From:*Alexander Arseniev [mailto:arseniev at btinternet.com]
> *Sent:* Wednesday, April 20, 2016 1:36 AM
> *To:* Aaron <aaron1 at gvtc.com>; juniper-nsp at puck.nether.net
> *Subject:* Re: [j-nsp] cgnat on service module - interesting bgp 
> advertisements
>
> Hello,
> MS-MIC (and MS-MPC NPUs as well) automatically cuts out network (in 
> your case .128) and broadcast (in your case .255) IPs.
> The rest cannot be expressed as single prefix, hence a bunch of 
> smaller prefixes is annonced instead.
> This was done as PR 1019354 fix
> https://prsearch.juniper.net/InfoCenter/index?page=prcontent&id=PR1019354
> HTH
> Thx
> Alex
>
> On 20/04/2016 00:48, Aaron wrote:
>
>     Very interesting. anyone know why this is happening ?  Is this documented ?
>
>     I put a /25 as the public nat pool, but look what this mx104 is advertising
>
>     via bgp.. It appears to chop up that /25 into a bunch of smaller subnets and
>
>     advertise those out
>
>       
>
>       
>
>     agould at eng-lab-mx104-cgn> show configuration | grep 1.2.3. | display set
>
>     set services nat pool nat1 address 1.2.3.128/25
>
>       
>
>       
>
>     agould at eng-lab-mx104-cgn> show route advertising-protocol bgp 10.101.0.2
>
>     table one.inet.0
>
>       
>
>     one.inet.0: 782 destinations, 970 routes (782 active, 0 holddown, 0 hidden)
>
>        Prefix                  Nexthop              MED     Lclpref    AS path
>
>     * 10.144.2.4/30           Self                         100        I
>
>     * 1.2.3.129/32         Self                         100        I
>
>     * 1.2.3.130/31         Self                         100        I
>
>     * 1.2.3.132/30         Self                         100        I
>
>     * 1.2.3.136/29         Self                         100        I
>
>     * 1.2.3.144/28         Self                         100        I
>
>     * 1.2.3.160/27         Self                         100        I
>
>     * 1.2.3.192/27         Self                         100        I
>
>     * 1.2.3.224/28         Self                         100        I
>
>     * 1.2.3.240/29         Self                         100        I
>
>     * 1.2.3.248/30         Self                         100        I
>
>     * 1.2.3.252/31         Self                         100        I
>
>     * 1.2.3.254/32         Self                         100        I
>
>       
>
>       
>
>     Aaron
>
>       
>
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