nginx 起動時の変な警告

awsでのデプロイを試みています。
nginxを起動すると、

nginx: [warn] conflicting server name "18.177.251.97" on 0.0.0.0:80, ignored

という警告が出てしまい、ページが表示できません。

nginx.conf.default

   include       mime.types;
    default_type  application/octet-stream;

    #log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
    #                  '$status $body_bytes_sent "$http_referer" '
    #                  '"$http_user_agent" "$http_x_forwarded_for"';

    #access_log  logs/access.log  main;

    sendfile        on;
    #tcp_nopush     on;

    #keepalive_timeout  0;
    keepalive_timeout  65;

    #gzip  on;

    server {
        listen       80;
        server_name  localhost;

        #charset koi8-r;

        #access_log  logs/host.access.log  main;

        location / {
            root   html;
            index  index.html index.htm;
        }

        #error_page  404              /404.html;

        # redirect server error pages to the static page /50x.html
        #
        error_page   500 502 503 504  /50x.html;
        location = /50x.html {
            root   html;
        }

nginx.conf

    keepalive_timeout   65;
    types_hash_max_size 2048;

    include             /etc/nginx/mime.types;
    default_type        application/octet-stream;

    # Load modular configuration files from the /etc/nginx/conf.d directory.
    # See http://nginx.org/en/docs/ngx_core_module.html#include
    # for more information.
    include /etc/nginx/conf.d/*.conf;

    index   index.html index.htm;

    server {
        listen       80 default_server;
        listen       [::]:80 default_server;
        server_name  18.177.251.97;
        root         /var/www/rails/sako_app/public;

        # Load configuration files for the default server block.
        include /etc/nginx/default.d/*.conf;

        location / {
        }

        # redirect server error pages to the static page /40x.html
        #
        error_page 404 /404.html;
            location = /40x.html {
        }

        # redirect server error pages to the static page /50x.html
        #
        error_page 500 502 503 504 /50x.html;
            location = /50x.html {
        }

/etc/nginx/conf.d/hoge_app

error_log  /var/www/rails/hoge_app/log/nginx.error.log;
access_log /var/www/rails/hoge_app/log/nginx.access.log;
# max body size
client_max_body_size 2G;
upstream app_server {
  # for UNIX domain socket setups
  server unix:/var/www/rails/hoge_app/tmp/sockets/.unicorn.sock fail_timeout=0;
}
server {
  listen 80;

  server_name 18.177.251.97;
  # nginx so increasing this is generally safe...
  keepalive_timeout 5;
  # path for static files
  root /var/www/rails/hoge_app/public;
  # page cache loading
  try_files $uri/index.html $uri.html $uri @app;
 location @app {
    # HTTP headers
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header Host $http_host;
    proxy_redirect off;
    proxy_pass http://app_server;
  }
  # Rails error pages
  error_page 500 502 503 504 /500.html;
  location = /500.html {
    root /var/www/rails/hoge_app/public;
  }
        location = /favicon.ico {
                   log_not_found off;
                  }
}

nginxの設定ファイルはこのようになっています。
設定ファイルに記入した、IPアドレス18.177.251.97が何かしらのIPと衝突してしまっているのかもしれないと考え、ポート80付近を探してみたのですが、原因が分かりません。どなたか原因が分かる方、いらっしゃいませんか？