I have two mik's connected by 3 or 4 routers and wireless radios,
call mikrp at the NOC and mikch out in the boonies. Wireless are Ubiquity Rockets running at over 100 megabits, and the routers inbetween are also miks. All
interfaces are 100 megabits, and all are clean of errors and drops.
Pings from mikrp to mikch shows about 10 to 20 ms but these pings do NOT
go over the EoIP.
PIngs to machines connected to mikch over the EoIP however are taking
200 to 400 msecs during 'heavy usage' time.
Usage is about 9 to 12 megabits download from mikrp to mikch which has
end users on it.
The results are dependable and repeatable every day during peak times. THe rest of
链接为空,如有no traffic on the link outside of the EoIP of significance.
THere is a second EoIP on the same link to yet another mik located after mikch,
and the ping times are also high there during peak times even though the
actual traffic on the EoIP is relatively low compared to the first EoIP.
This indicates that traffic on one link is enough to trouble both links, all the while
pings directly between miks remains low at all times.
mikrp -------- mikch ---------mikth
| |
customers customers
EoIP from mikrp to mikch
Eoip from mikrp to mikth
An ethernet bridge is created between mikrp and mikch and bridged so that
mikrp is a bridged extension of mikch.
The manual says the MTU of the EoIP and the bridge should be left at 1500 to
prevent fragmentation.
However the manual also says that the EoIP process adds 42 bytes to the
1500 bytes packet, 8 GRE, 20 IP, and 14 ethernet.
Since packets come into mikrp at 1500 like any other router, and mikrp
adds 42 bytes to the packet before putting it on the EoIP, it would seem
that fragmentation would have to happen at that point before putting the packet
on the EoIP.
However if the EoIP is set to 1458, then added 42 bytes makes it 1500 and
it fits on the EoIP without frag.
However since the packet came into mikrp at 1500 in the first place, it will clearly
need to be fragged to match the new 1458, so whether the MTU of the EoIP
is changed from 1500 to 1458 or not, does not change the fact that packets
will be fragged before being put on EoIP.
Is that right?
Further if the MTU of the EoIP is set to 1542, then the packets can go directly
onto the EoIP without fragging, but must be fragged before egressing that
router at 1500 on its way to the remote end of the EoIP tunnel.
Is that right?
Homer