Deployment Guide
39 VxFlex Network Deployment Guide using Dell EMC Networking 25GbE switches and OS9
B Routing VxFlex Virtual Machine traffic
In this section a possible solution to solve routing between SVMs in separate subnets is outlined. Each SVM
contains three virtual NICs:
• Eth0 for VxFlex management
• Eth1 for VxFlex Data01
• Eth2 for VxFlex Data02
The SVM uses a single TCP/IP stack, and any unknown networks are limited to this single default gateway. If
VxFlex Data01 or VxFlex Data02 needs to reach an SVM in another subnet, for instance in another rack in
the data center, this traffic fails. Each SVM in the environment can be updated to leverage policy-based
routing (PBR).
3. To show the routing table of an SVM issue the command ip route.
ScaleIO-172-16-33-12:~ # ip route
default via 172.16.33.253 dev eth0
127.0.0.0/8 dev lo scope link
169.254.0.0/16 dev eth0 scope link
172.16.33.0/24 dev eth0 proto kernel scope link src 172.16.33.12
172.16.34.0/24 dev eth1 proto kernel scope link src 172.16.34.12
172.16.35.0/24 dev eth2 proto kernel scope link src 172.16.35.12
4. When attempting to ping the SVM from another network, the ping fails due to asymmetric routing. The
ping reaches the host as shown by TCP dump.
ScaleIO-172-16-33-12:~ # tcpdump -n -i eth1 icmp
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth1, link-type EN10MB (Ethernet), capture size 96 bytes
22:43:40.067441 IP 172.18.31.101 > 172.16.34.12: ICMP echo request, id 56600,
seq 0, length 64
22:43:41.067630 IP 172.18.31.101 > 172.16.34.12: ICMP echo request, id 56600,
seq 1, length 64
22:43:42.069783 IP 172.18.31.101 > 172.16.34.12: ICMP echo request, id 56600,
seq 2, length 64
5. However, due to the routing table, the response is sent back out eth0 resulting in a failed connection.
To address this problem, create two routing tables for eth1 and eth2 and verify that they have been
created.
ScaleIO-172-16-33-12:~ # echo '100 eth1' >> /etc/iproute2/rt_tables && echo '200
eth2' >> /etc/iproute2/rt_tables && cat /etc/iproute2/rt_tables
# reserved values
#
255 local
254 main
253 default
0 unspec
#
# local