Subnet reservation

Available subnets

Each site of Grid'5000 is allocated a /14 ip block giving thus a total of 262142 different IPs. Therefore, the maximum range of IPs has to be in this /14 subnet.

The /14 address block available on each site is divided in four /16 blocks as described here. The last two /16 blocks are used for IP reservation through OAR. Because they are contiguous, we can see them as a single /15 block where the last 2 IPs are reserved for Grid'5000 infrastructure. Therefore, the reservable range of IPs is composed of a total of 131070 - 2 = 131068 IPs.

Concerning the smallest subnet size, it is a /22, which is equivalent to 1022 hosts per subnet. We do not allow smaller subnets to avoid a scheduling overhead in OAR. The /15 block contains 128 reservable /22 subnets.

Requesting subnets

Subnet reservation through OAR is similar to normal resource reservation.

To reserve 4 /21 subnets and 2 nodes, just type:

frontend:

oarsub -l {"type='subnet'"}/slash_21=4+/nodes=2 -I

You can of-course have more complex request. To obtain 4 /21 on different /20 subnets, you can type:

frontend:

oarsub -l {"type='subnet'"}/slash_20=4/slash_21=1+/nodes=2/core=1 -I

Getting your networks

The simplest way to get the list of your allocated subnets is to use the "get_subnets" script provided on the head node of the submission.

# get_subnets
10.8.0.0
10.8.8.0

The "-p" options prints the CIDR format

# get_subnets -p
10.8.0.0/21
10.8.8.0/21

You can also compress the subnets into a larger one if they are contiguous:

# get_subnets -pc
10.8.0.0/22

However, when not contiguous, the networks are not merged.

# get_subnets -p
10.8.0.0/21
10.8.16.0/21
# get_subnets -pc
10.8.0.0/21
10.8.16.0/21