アップデートしたらすんなり繋がりました(゜Д゜)
原因が何かさっぱり分からない状態ということになるので、これはこれで凄い気持ち悪いですね。。
M3CSLさん、長々とありがとうございました。
最後に接続できたときのログをつけておきます。
---- 接続テストのMacBook ----
Fri Feb 3 18:44:14 2012 : L2TP connecting to server 'MacMiniさん' (210.xxx.xxx.102)...
Fri Feb 3 18:44:14 2012 : IPSec connection started
Fri Feb 3 18:44:15 2012 : IPSec connection established
Fri Feb 3 18:44:15 2012 : L2TP connection established.
Fri Feb 3 18:44:15 2012 : Using interface ppp0
Fri Feb 3 18:44:15 2012 : Connect: ppp0 <--> socket[34:18]
Fri Feb 3 18:44:15 2012 : route_interface: write routing socket failed, File exists. (address 10.0.1.0, mask 255.255.255.0, interface ppp0, host 0).
Fri Feb 3 18:44:15 2012 : local IP address 10.0.1.80
Fri Feb 3 18:44:15 2012 : remote IP address 210.xxx.xxx.102
Fri Feb 3 18:44:15 2012 : primary DNS address プライマリDNSアドレス
Fri Feb 3 18:44:15 2012 : secondary DNS address セカンダリDNSアドレス
Fri Feb 3 18:44:15 2012 : l2tp_wait_input: Address added. previous interface setting (name: en0, address: 10.0.1.2), current interface setting (name: ppp0, family: PPP, address: 10.0.1.80, subnet: 255.0.0.0, destination: 210.xxx.xxx.102).
---- 接続先MacMiniさん ----
Fri Feb 3 18:44:15 2012 : Directory Services Authentication plugin initialized
Fri Feb 3 18:44:15 2012 : Directory Services Authorization plugin initialized
Fri Feb 3 18:44:15 2012 : L2TP incoming call in progress from '接続元のグローバルIP'...
Fri Feb 3 18:44:15 2012 : L2TP received SCCRQ
Fri Feb 3 18:44:15 2012 : L2TP sent SCCRP
Fri Feb 3 18:44:15 2012 : L2TP received SCCCN
Fri Feb 3 18:44:15 2012 : L2TP received ICRQ
Fri Feb 3 18:44:15 2012 : L2TP sent ICRP
Fri Feb 3 18:44:15 2012 : L2TP received ICCN
Fri Feb 3 18:44:15 2012 : L2TP connection established.
Fri Feb 3 18:44:15 2012 : using link 0
Fri Feb 3 18:44:15 2012 : Using interface ppp0
Fri Feb 3 18:44:15 2012 : Connect: ppp0 <--> socket[34:18]
Fri Feb 3 18:44:15 2012 : sent [LCP ConfReq id=0x1 <asyncmap 0x0> <auth chap MS-v2> <magic 0x3a12c14c> <pcomp> <accomp>]
Fri Feb 3 18:44:15 2012 : rcvd [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0x6db22790> <pcomp> <accomp>]
Fri Feb 3 18:44:15 2012 : lcp_reqci: returning CONFACK.
Fri Feb 3 18:44:15 2012 : sent [LCP ConfAck id=0x1 <asyncmap 0x0> <magic 0x6db22790> <pcomp> <accomp>]
Fri Feb 3 18:44:15 2012 : rcvd [LCP ConfAck id=0x1 <asyncmap 0x0> <auth chap MS-v2> <magic 0x3a12c14c> <pcomp> <accomp>]
Fri Feb 3 18:44:15 2012 : sent [LCP EchoReq id=0x0 magic=0x3a12c14c]
Fri Feb 3 18:44:15 2012 : sent [CHAP Challenge id=0xea <473d35485c513139226333293604782a>, name = "MacMiniさん"]
Fri Feb 3 18:44:15 2012 : rcvd [LCP EchoReq id=0x0 magic=0x6db22790]
Fri Feb 3 18:44:15 2012 : sent [LCP EchoRep id=0x0 magic=0x3a12c14c]
Fri Feb 3 18:44:15 2012 : rcvd [LCP EchoRep id=0x0 magic=0x6db22790]
Fri Feb 3 18:44:15 2012 : rcvd [CHAP Response id=0xea <208ced73cbf4b7dcaf39c641d1e2c2710000000000000000d745a32c3f608747987fdeea677c47652dd5b902c3b0a8f900>, name = "ユーザー名"]
Fri Feb 3 18:44:15 2012 : DSAuth plugin: unsupported authen authority: recved Kerberosv5;;ユーザー名@LKDC:SHA1.8508D7109DFDCBED8F218B74DC970817522A5BF4;LKDC:SHA1.8508D7109DFDCBED8F218B74DC970817522A5BF4, want ApplePasswordServer
Fri Feb 3 18:44:15 2012 : sent [CHAP Success id=0xea "S=467597AD3DB835389F5D75B2CCD54B325C7C3A97 M=Access granted"]
Fri Feb 3 18:44:15 2012 : CHAP peer authentication succeeded for tunashima
Fri Feb 3 18:44:15 2012 : DSAccessControl plugin: User 'ユーザー名' authorized for access
Fri Feb 3 18:44:15 2012 : sent [IPCP ConfReq id=0x1 <addr 210.xxx.xxx.102>]
Fri Feb 3 18:44:15 2012 : sent [ACSCP ConfReq id=0x1]
Fri Feb 3 18:44:15 2012 : rcvd [IPCP ConfReq id=0x1 <addr 0.0.0.0> <ms-dns1 0.0.0.0> <ms-dns3 0.0.0.0>]
Fri Feb 3 18:44:15 2012 : ipcp: returning Configure-NAK
Fri Feb 3 18:44:15 2012 : sent [IPCP ConfNak id=0x1 <addr 10.0.1.80> <ms-dns1 プライマリDNSアドレス> <ms-dns3 セカンダリDNSアドレス>]
Fri Feb 3 18:44:15 2012 : rcvd [IPV6CP ConfReq id=0x1 <addr fe80::0225:00ff:fecc:df64>]
Fri Feb 3 18:44:15 2012 : Unsupported protocol 0x8057 received
Fri Feb 3 18:44:15 2012 : sent [LCP ProtRej id=0x2 80 57 01 01 00 0e 01 0a 02 25 00 ff fe cc df 64]
Fri Feb 3 18:44:15 2012 : rcvd [ACSCP ConfReq id=0x1 <route vers 16777216> <domain vers 16777216>]
Fri Feb 3 18:44:15 2012 : sent [ACSCP ConfRej id=0x1 <route vers 16777216>]
Fri Feb 3 18:44:15 2012 : rcvd [IPCP ConfAck id=0x1 <addr 210.xxx.xxx.102>]
Fri Feb 3 18:44:15 2012 : rcvd [ACSCP ConfAck id=0x1]
Fri Feb 3 18:44:15 2012 : rcvd [IPCP ConfReq id=0x2 <addr 10.0.1.80> <ms-dns1 プライマリDNSアドレス> <ms-dns3 セカンダリDNSアドレス>]
Fri Feb 3 18:44:15 2012 : ipcp: returning Configure-ACK
Fri Feb 3 18:44:15 2012 : sent [IPCP ConfAck id=0x2 <addr 10.0.1.80> <ms-dns1 プライマリDNSアドレス> <ms-dns3 セカンダリDNSアドレス>]
Fri Feb 3 18:44:15 2012 : ipcp: up
Fri Feb 3 18:44:15 2012 : found interface en1 for proxy arp
Fri Feb 3 18:44:15 2012 : local IP address 210.xxx.xxx.102
Fri Feb 3 18:44:15 2012 : remote IP address 10.0.1.80
Fri Feb 3 18:44:15 2012 : l2tp_wait_input: Address added. previous interface setting (name: en0, address: 210.xxx.xxx.102), current interface setting (name: ppp0, family: PPP, address: 210.xxx.xxx.102, subnet: 255.255.255.xxx, destination: 10.0.1.80).
Fri Feb 3 18:44:15 2012 : rcvd [ACSCP ConfReq id=0x2 <domain vers 16777216>]
Fri Feb 3 18:44:15 2012 : sent [ACSCP ConfAck id=0x2 <domain vers 16777216>]
Fri Feb 3 18:44:15 2012 : sent [ACSP data <payload len 18, packet seq 0, CI_DOMAINS, flags: START END REQUIRE-ACK>
<domain: name ドメイン名>]
Fri Feb 3 18:44:15 2012 : rcvd [IP data <src addr 10.0.1.80> <dst addr 255.255.255.255> <BOOTP Request> <type INFORM> <client id 0x08000000010000> <parameters = 0x6 0x2c 0x2b 0x1 0xf9 0xf>]
Fri Feb 3 18:44:15 2012 : sent [IP data <src addr 210.xxx.xxx.102> <dst addr 10.0.1.80> <BOOTP Reply> <type ACK> <server id 0xd2e6fcc3> <domain name "ドメイン名">]
Fri Feb 3 18:44:15 2012 : rcvd [ACSP data <payload len 0, packet seq 0, CI_DOMAINS, flags: ACK>]