Multihoming confusion
fedora at ayni.com
fedora at ayni.com
Sun Jan 31 13:05:01 UTC 2010
Hi HW
thank you very much, that helps.
I was before on a page describing this advanced routing, however, the main
title there was "Load Sharing and Performance increase", which is not,
what I sought. So I let it off.
suomi
> On Sun, Jan 31, 2010 at 12:05 PM, <fedora at ayni.com> wrote:
>> Hi every
>>
>> I am changing the ISP from aaa.bbb.243.160/27 to ccc.ddd.206.128/27.
>> In order to provide seamless service to our customers I made the hosts
>> concerned multihomed, i.e. I added them a logical interface on the new
>> subnet. I did not introduce a additional NIC into the hosts.
>> Then, I changed the default route on the hosts to the new network.
>>
>> e.g in one host concerned you will see
>>
>> myhost:~ # ifconfig
>> eth0 Link encap:Ethernet HWaddr 00:80:AD:B8:39:C3
>> inet addr:ccc.ddd.206.132 Bcast:aaa.bbb.243.191
>> Mask:255.255.255.224
>> inet6 addr: fe80::80:adb8:39c3/10 Scope:Link
>> inet6 addr: fe80::280:adff:feb8:39c3/10 Scope:Link
>> UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
>> RX packets:2733080 errors:0 dropped:0 overruns:0 frame:0
>> TX packets:2494806 errors:0 dropped:0 overruns:0 carrier:0
>> collisions:119322 txqueuelen:100
>> RX bytes:791914000 (755.2 Mb) TX bytes:579375282 (552.5 Mb)
>> Interrupt:9 Base address:0xf000
>>
>> eth0:1 Link encap:Ethernet HWaddr 00:80:AD:B8:39:C3
>> inet addr:192.168.97.164 Bcast:192.168.97.255
>> Mask:255.255.255.0
>> UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
>> Interrupt:9 Base address:0xf000
>>
>> eth0:2 Link encap:Ethernet HWaddr 00:80:AD:B8:39:C3
>> inet addr:aaa.bbb.243.164 Bcast:ccc.ddd.206.159
>> Mask:255.255.255.224
>> UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
>> Interrupt:9 Base address:0xf000
>>
>> lo Link encap:Local Loopback
>> inet addr:127.0.0.1 Mask:255.0.0.0
>> inet6 addr: ::1/128 Scope:Host
>> UP LOOPBACK RUNNING MTU:16436 Metric:1
>> RX packets:372918 errors:0 dropped:0 overruns:0 frame:0
>> TX packets:372918 errors:0 dropped:0 overruns:0 carrier:0
>> collisions:0 txqueuelen:0
>> RX bytes:92340116 (88.0 Mb) TX bytes:92340116 (88.0 Mb)
>>
>> myhost:~ #
>>
>> and
>>
>> myhost:~ # route -n
>> Kernel IP routing table
>> Destination Gateway Genmask Flags Metric Ref Use
>> Iface
>> aaa.bbb.243.160 0.0.0.0 255.255.255.224 U 0 0 0
>> eth0
>> ccc.ddd.206.128 0.0.0.0 255.255.255.224 U 0 0 0
>> eth0
>> 192.168.97.0 0.0.0.0 255.255.255.0 U 0 0 0
>> eth0
>> 0.0.0.0 ccc.ddd.206.129 0.0.0.0 UG 0 0 0
>> eth0
>> myhost:~ #
>>
>> NOTE: this multihoming has nothing to do with additional security or
>> performance.
>>
>> I did not install something with iproute2 or other routing enhancements.
>>
>> PROBLEM: the multihoming works only partially.
>>
>> if I invoke e.g. ping on http://iptools.com/ the ping reply does not
>> come
>> back to its origin. The echo request reaches my server, my server sends
>> an
>> echo reply, which never reaches the originator.
>>
>>
>> myhost:~ # tcpdump -n ip proto \\icmp
>> Kernel filter, protocol ALL, datagram packet socket
>> tcpdump: listening on eth0
>> 10:58:35.508765 74.52.9.36 > aaa.bbb.243.164: icmp: echo request (DF)
>> 10:58:35.508765 aaa.bbb.243.164 > 74.52.9.36: icmp: echo reply (DF)
>> 10:58:36.508765 74.52.9.36 > aaa.bbb.243.164: icmp: echo request (DF)
>> 10:58:36.508765 aaa.bbb.243.164 > 74.52.9.36: icmp: echo reply (DF)
>> 10:58:37.508765 74.52.9.36 > aaa.bbb.243.164: icmp: echo request (DF)
>> 10:58:37.508765 aaa.bbb.243.164 > 74.52.9.36: icmp: echo reply (DF)
>> 10:58:38.508765 74.52.9.36 > aaa.bbb.243.164: icmp: echo request (DF)
>> 10:58:38.508765 aaa.bbb.243.164 > 74.52.9.36: icmp: echo reply (DF)
>> 10:58:39.508765 74.52.9.36 > aaa.bbb.243.164: icmp: echo request (DF)
>> 10:58:39.508765 aaa.bbb.243.164 > 74.52.9.36: icmp: echo reply (DF)
>> ...
>>
>> on http://iptools.com/ :
>> PING aaa.bbb.243.164 (aaa.bbb.243.164) 56(84) bytes of data.
>>
>> --- aaa.bbb.243.164 ping statistics ---
>> 5 packets transmitted, 0 received, 100% packet loss, time 3999ms
>>
>>
>>
>> If, however, I ping the Host on the other (the new) network address from
>> http://iptools.com/, the ping gets through:
>>
>>
>> myhost:~ # tcpdump -n ip proto \\icmp
>> Kernel filter, protocol ALL, datagram packet socket
>> tcpdump: listening on eth0
>> 11:23:04.117248 74.52.9.36 > ccc.ddd.206.132: icmp: echo request (DF)
>> 11:23:04.117248 ccc.ddd.206.132 > 74.52.9.36: icmp: echo reply (DF)
>> 11:23:05.117248 74.52.9.36 > ccc.ddd.206.132: icmp: echo request (DF)
>> 11:23:05.117248 ccc.ddd.206.132 > 74.52.9.36: icmp: echo reply (DF)
>> 11:23:06.117248 74.52.9.36 > ccc.ddd.206.132: icmp: echo request (DF)
>> 11:23:06.117248 ccc.ddd.206.132 > 74.52.9.36: icmp: echo reply (DF)
>> 11:23:07.117248 74.52.9.36 > ccc.ddd.206.132: icmp: echo request (DF)
>> 11:23:07.117248 ccc.ddd.206.132 > 74.52.9.36: icmp: echo reply (DF)
>> 11:23:08.117248 74.52.9.36 > ccc.ddd.206.132: icmp: echo request (DF)
>> 11:23:08.117248 ccc.ddd.206.132 > 74.52.9.36: icmp: echo reply (DF)
>>
>> on http://iptools.com/
>>
>> PING ccc.ddd.206.132 (ccc.ddd.206.132) 56(84) bytes of data.
>> 64 bytes from ccc.ddd.206.132: icmp_seq=1 ttl=245 time=132 ms
>> 64 bytes from ccc.ddd.206.132: icmp_seq=2 ttl=245 time=132 ms
>> 64 bytes from ccc.ddd.206.132: icmp_seq=3 ttl=245 time=133 ms
>> 64 bytes from ccc.ddd.206.132: icmp_seq=4 ttl=245 time=132 ms
>> 64 bytes from ccc.ddd.206.132: icmp_seq=5 ttl=245 time=132 ms
>>
>> --- ccc.ddd.206.132 ping statistics ---
>> 5 packets transmitted, 5 received, 0% packet loss, time 4000ms
>> rtt min/avg/max/mdev = 132.915/132.980/133.114/0.405 m
>>
>> If I ping the iptools.com host from my host:
>>
>> myhost:~ # ping 74.52.9.36
>> PING 74.52.9.36 (74.52.9.36): 56 data bytes
>> 64 bytes from 74.52.9.36: icmp_seq=0 ttl=54 time=134.925 ms
>> 64 bytes from 74.52.9.36: icmp_seq=1 ttl=54 time=133.172 ms
>> 64 bytes from 74.52.9.36: icmp_seq=2 ttl=54 time=133.426 ms
>> 64 bytes from 74.52.9.36: icmp_seq=3 ttl=54 time=133.735 ms
>> 64 bytes from 74.52.9.36: icmp_seq=4 ttl=54 time=133.503 ms
>> --- 74.52.9.36 ping statistics ---
>> 5 packets transmitted, 5 packets received, 0% packet loss
>> round-trip min/avg/max = 133.172/133.752/134.925 ms
>> myhost:~ #
>>
>> Summary: If, on my host, a service is called for on the old
>> (aaa.bbb.243.160/27) network, it is not properly answered on the new
>> network (ccc.ddd.206.128/27).
>>
>> I also tried to enable IP forwarding on this host
>>
>> myhost:~ # !493
>> echo "1" > /proc/sys/net/ipv4/ip_forward
>> myhost:~ # cat /proc/sys/net/ipv4/ip_forward
>> 1
>> myhost:~ #
>>
>> but this did not change anything either.
>> Furthermore, I was informed on my googling around, that IP forwarding
>> must
>> not be enabled on a multihomed host.
>>
>> What did I miss?
>>
>
> You need to correct the routing, see
> http://tldp.org/HOWTO/Adv-Routing-HOWTO/lartc.rpdb.multiple-links.html
>
> //HW
>
>> Thanks for any hints.
>>
>> suomi
>>
>>
>>
>>
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