[j-nsp] Subscriber DHCPv6 lease time for IA_NA from Radius Server
Wojciech Janiszewski
wojciech.janiszewski at gmail.com
Wed Mar 11 06:42:31 EDT 2020
Hi Sebastian,
If I remember correctly, DHCP Lease Time can be adjusted by using Radius
Session-Timeout attribute.
Regards,
Wojciech
śr., 11 mar 2020 o 11:32 Sebastian Wiesinger <sebastian at karotte.org>
napisał(a):
> Hi,
>
> I'm currently testing IPv6 subscriber termination (PPP/L2TP) on an
> MX204 (18.4R2) and I have a bit of a problem with DHCPv6 IA_NA address
> allocation.
>
> By default the lease time for the address is one day (86400 seconds)
> when the address is received by Radius.
>
> The Cisco CPE configures this address on the Dialer interface which
> does not go down when the PPP session is cleared. So the address stays
> there for a day at least which is suboptimal.
>
> We want to reduce the lease time so that it is detected sooner that
> the address is invalid and can be released / reused.
>
> The only way to change this behaviour seems to be setting the
> 'asymmetric-lease-time' option in the dhcpv6 group overrides. I set it
> to 600 seconds which works as expected (address has a lifetime of 600
> seconds) BUT the MX does not respond to rebind queries from the
> client. So the address times out and the client has to solicit the
> address again.
>
> Traceoptions seem to indicate that the packet is handled in an special
> way because of the asymmetric lease time:
>
> Mar 11 10:58:56.881706 [MSTR][DEBUG] dhcpv6_packet_new: PACKET - Allocated
> new v6 packet 0xa176480
> Mar 11 10:58:56.881749 [MSTR][INFO]
> [default:default][SVR][INET6][si-0/0/0.3221225603] >>>>>>>>>> Decode
> message from == fe80::12f3:11ff:fe81:18fe/546 <<<<<<<<<<
> Mar 11 10:58:56.881760 [MSTR][INFO]
> [default:default][SVR][INET6][si-0/0/0.3221225603] --[ msgtype ==
> DHCPV6-REBIND ]--------------------------
> Mar 11 10:58:56.881769 [MSTR][INFO]
> [default:default][SVR][INET6][si-0/0/0.3221225603] --[ len == 76 ]--
> Mar 11 10:58:56.881778 [MSTR][INFO]
> [default:default][SVR][INET6][si-0/0/0.3221225603] --[ xid == e72bcf ]--
> Mar 11 10:58:56.881787 [MSTR][INFO]
> [default:default][SVR][INET6][si-0/0/0.3221225603] --[ Internally
> Unsupported Option
> Mar 11 10:58:56.881799 [MSTR][INFO]
> [default:default][SVR][INET6][si-0/0/0.3221225603] OPTION code 8,
> len 2, data 00 00 ]--
> Mar 11 10:58:56.881808 [MSTR][INFO]
> [default:default][SVR][INET6][si-0/0/0.3221225603] --[ OPTION_CLIENTID
> Mar 11 10:58:56.881820 [MSTR][INFO]
> [default:default][SVR][INET6][si-0/0/0.3221225603] OPTION code 1,
> len 10, data 00 03 00 01 10 f3 11 81 18 fe ]--
> Mar 11 10:58:56.881829 [MSTR][INFO]
> [default:default][SVR][INET6][si-0/0/0.3221225603] --[ OPTION_OPT_REQ
> Mar 11 10:58:56.881839 [MSTR][INFO]
> [default:default][SVR][INET6][si-0/0/0.3221225603] OPTION code 6,
> len 4, data 00 17 00 18 ]--
> Mar 11 10:58:56.881848 [MSTR][INFO]
> [default:default][SVR][INET6][si-0/0/0.3221225603] --[ OPTION_IA_NA
> Mar 11 10:58:56.881856 [MSTR][INFO]
> [default:default][SVR][INET6][si-0/0/0.3221225603] OPTION code 3,
> len 40, iaid 1114113, T1 0, T2 0 ]--
> Mar 11 10:58:56.881866
> [MSTR][DEBUG][default:default][SVR][INET6][si-0/0/0.3221225603]
> dhcpv6_option_parse: Parsing suboptions of OPTION_IA_NA - Start
> Mar 11 10:58:56.881875 [MSTR][INFO]
> [default:default][SVR][INET6][si-0/0/0.3221225603] --[ OPTION_IAADDR
> Mar 11 10:58:56.881885 [MSTR][INFO]
> [default:default][SVR][INET6][si-0/0/0.3221225603] OPTION code 5,
> len 24, pre-ltime 600, valid-ltime 600, addr 2001:db8:8:1d::1, data NULL
> ]--
> Mar 11 10:58:56.881895
> [MSTR][DEBUG][default:default][SVR][INET6][si-0/0/0.3221225603]
> dhcpv6_option_parse: Parsing suboptions of OPTION_IA_NA - Done
> Mar 11 10:58:56.881905
> [MSTR][DEBUG][default:default][SVR][INET6][si-0/0/0.3221225603]
> dhcpv6_packet_decode: dhcpv6 pkt parsing - End
> Mar 11 10:58:56.881914 [MSTR][DEBUG] dhcpv6_packet_handle: ALQ: LQ update
> skipped - Not expected
> Mar 11 10:58:56.881926
> [MSTR][DEBUG][default:default][SVR][INET6][si-0/0/0.3221225603]
> jdhcpd_v6_short_lease_recv_check: Checking packet safd for short lease
> requirement
> Mar 11 10:58:56.881935
> [MSTR][DEBUG][default:default][SVR][INET6][si-0/0/0.3221225603]
> jdhcpd_v6_short_lease_recv_check: Packet safd has short lease configuration
> call short lease handler
> Mar 11 10:58:56.881952
> [MSTR][DEBUG][default:default][SVR][INET6][si-0/0/0.3221225603]
> jdhcpd_v6_short_lease_recv_check: Packet converted returning to sender
> Mar 11 10:58:56.881987
> [MSTR][DEBUG][default:default][SVR][INET6][si-0/0/0.3221225603]
> jdhcpd_v6_short_lease_recv_check: Short lease refreshed
> Mar 11 10:58:56.881997
> [MSTR][DEBUG][default:default][SVR][INET6][si-0/0/0.3221225603]
> dhcpv6_packet_handle: Short lease processing has consumed this packet
> Mar 11 10:58:56.882008
> [MSTR][DEBUG][default:default][SVR][INET6][si-0/0/0.3221225603]
> dhcpv6_packet_handle: leasequeryreply No, retries 0
> Mar 11 10:58:56.882016 [MSTR][DEBUG] dhcpv6_packet_free: PACKET - Freeing
> v6 packet 0xa176480
>
> The trace says "Short lease refreshed" but no reply is sent to the
> client. Any idea how this can be solved? It seems one can only
> configure lease times when using a IPv6 pool, but we use addresses
> configured from Radius.
>
> Config looks like this:
>
> # show system services dhcp-local-server
> dhcpv6 {
> group lns-dhcpv6 {
> overrides {
> rapid-commit;
> asymmetric-lease-time 600;
> asymmetric-prefix-lease-time 600;
> }
> interface si-0/0/0.0;
> interface si-0/1/0.0;
> }
> }
>
> Radius has:
>
> Framed-IPv6-Prefix = "2001:db8:8:1d::1/128"
>
> And Cisco CPE uses this:
>
> interface Dialer7
> mtu 1448
> ip address negotiated
> ip virtual-reassembly in
> encapsulation ppp
> load-interval 30
> dialer pool 7
> no cdp enable
> ipv6 address dhcp rapid-commit
> ipv6 enable
> no ipv6 redirects
> ppp authentication chap callin
> ppp chap hostname ********
> ppp chap password 0 ******
> ppp pap refuse
> !
>
> Best Regards
>
> Sebastian
>
> --
> GPG Key: 0x58A2D94A93A0B9CE (F4F6 B1A3 866B 26E9 450A 9D82 58A2 D94A 93A0
> B9CE)
> 'Are you Death?' ... IT'S THE SCYTHE, ISN'T IT? PEOPLE ALWAYS NOTICE THE
> SCYTHE.
> -- Terry Pratchett, The Fifth Elephant
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