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new 0094a6c Update with multicast limit note for vxlan
0094a6c is described below
commit 0094a6cd94cac8d51ed7e3ff6de1e5b60605d7f9
Author: Andrija Panic <[email protected]>
AuthorDate: Thu Nov 9 14:02:49 2017 +0100
Update with multicast limit note for vxlan
igmp_max_memberships must be increased to allow more than 20 mutlicast IPs
(vxlan interfaces) per host
---
rtd/source/networking/vxlan.rst | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/rtd/source/networking/vxlan.rst b/rtd/source/networking/vxlan.rst
index dcd6b7e..67eff6a 100644
--- a/rtd/source/networking/vxlan.rst
+++ b/rtd/source/networking/vxlan.rst
@@ -87,6 +87,16 @@ have MTU of 1500 bytes, meaning that your physical
interface/bridge must have MT
In order to configure "jumbo frames" you can i.e. make physical
interface/bridge with 9000 bytes MTU, then all the vxlan
interfaces will be created with MTU of 8950 bytes, and then MTU size inside VM
can be set to 8950 bytes.
+Important note on max number of multicast groups (and thus VXLAN intefaces)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Default value of "net.ipv4.igmp_max_memberships" (cat
/proc/sys/net/ipv4/igmp_max_memberships) is "20", which means that host can be
joined to max 20 multicast groups (attach max 20 multicast IPs on the host).
+Since all VXLAN (VTEP) interfaces provisioned on host are multicast-based
(belong to certain multicast group, and thus has it's own multicast IP that is
used as VTEP), this means that you can not provision more than 20 (working)
VXLAN interfaces per host.
+On Linux kernel 3.x you actually can provision more than 20, but ARP request
will silently fail and cause client's networking problems
+On Linux kernel 4.x you can NOT provision (start) more than 20 VXLAN
interfaces and error message "No buffer space available" can be observed in
Cloudstack Agent logs after provisioning required bridges and VXLAN interfaces.
+Increase needed parameter to sane value (i.e. 100 or 200) as required.
+If you need to operate more than 20 VMs from different client's network, this
change above is required.
+
Advanced: Build kernel and iproute2
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